Skip to main content
\(\require{cancel}\)
Physics LibreTexts

Glossary

  • Page ID
    29419
  • Example and Directions
    Words (or words that have the same definition) The definition is case sensitive (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] (Optional) Caption for Image (Optional) External or Internal Link (Optional) Source for Definition
    (Eg. "Genetic, Hereditary, DNA ...") (Eg. "Relating to genes or heredity") The infamous double helix https://bio.libretexts.org/ CC-BY-SA; Delmar Larsen
    Glossary Entries
    Word(s) Definition Image Caption Link Source
    accuracy the degree to which a measured value agrees with correct value for that measurement
    approximation an estimated value based on prior experience and reasoning
    classical physics physics that was developed from the Renaissance to the end of the 19th century
    conversion factor a ratio expressing how many of one unit are equal to another unit
    derived units units that can be calculated using algebraic combinations of the fundamental units
    English units system of measurement used in the United States; includes units of measurement such as feet, gallons, and pounds
    fundamental units units that can only be expressed relative to the procedure used to measure them
    kilogram the SI unit for mass, abbreviated (kg)
    law a description, using concise language or a mathematical formula, a generalized pattern in nature that is supported by scientific evidence and repeated experiments
    meter the SI unit for length, abbreviated (m)
    method of adding percents the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation
    metric system a system in which values can be calculated in factors of 10
    model representation of something that is often too difficult (or impossible) to display directly
    modern physics the study of relativity, quantum mechanics, or both
    order of magnitude refers to the size of a quantity as it relates to a power of 10
    percent uncertainty the ratio of the uncertainty of a measurement to the measured value, expressed as a percentage
    physical quantity a characteristic or property of an object that can be measured or calculated from other measurements
    physics the science concerned with describing the interactions of energy, matter, space, and time; it is especially interested in what fundamental mechanisms underlie every phenomenon
    precision the degree to which repeated measurements agree with each other
    quantum mechanics the study of objects smaller than can be seen with a microscope
    relativity the study of objects moving at speeds greater than about 1% of the speed of light, or of objects being affected by a strong gravitational field
    scientific method a method that typically begins with an observation and question that the scientist will research; next, the scientist typically performs some research about the topic and then devises a hypothesis; then, the scientist will test the hypothesis by performing an experiment; finally, the scientist analyzes the results of the experiment and draws a conclusion
    second the SI unit for time, abbreviated (s)
    SI units the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams
    significant figures express the precision of a measuring tool used to measure a value
    theory an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers
    uncertainty a quantitative measure of how much your measured values deviate from a standard or expected value
    units a standard used for expressing and comparing measurements
    acceleration the rate of change in velocity; the change in velocity over time
    acceleration due to gravity acceleration of an object as a result of gravity
    average acceleration the change in velocity divided by the time over which it changes
    average speed distance traveled divided by time during which motion occurs
    average velocity displacement divided by time over which displacement occurs
    deceleration acceleration in the direction opposite to velocity; acceleration that results in a decrease in velocity
    dependent variable the variable that is being measured; usually plotted along the ysize 12{y} {}-axis
    displacement the change in position of an object
    distance the magnitude of displacement between two positions
    distance traveled the total length of the path traveled between two positions
    elapsed time the difference between the ending time and beginning time
    free-fall the state of movement that results from gravitational force only
    independent variable the variable that the dependent variable is measured with respect to; usually plotted along the xsize 12{x} {}-axis
    instantaneous acceleration acceleration at a specific point in time
    instantaneous speed magnitude of the instantaneous velocity
    instantaneous velocity velocity at a specific instant, or the average velocity over an infinitesimal time interval
    kinematics the study of motion without considering its causes
    model simplified description that contains only those elements necessary to describe the physics of a physical situation
    position the location of an object at a particular time
    scalar a quantity that is described by magnitude, but not direction
    slope the difference in ysize 12{y} {}-value (the rise) divided by the difference in xsize 12{x} {}-value (the run) of two points on a straight line
    time change, or the interval over which change occurs
    vector a quantity that is described by both magnitude and direction
    y-intercept the y-size 12{y} {}value when xsize 12{x} {}= 0, or when the graph crosses the ysize 12{y} {}-axis
    air resistance a frictional force that slows the motion of objects as they travel through the air; when solving basic physics problems, air resistance is assumed to be zero
    analytical method the method of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trigonometric identities
    classical relativity the study of relative velocities in situations where speeds are less than about 1% of the speed of light—that is, less than 3000 km/s
    commutative refers to the interchangeability of order in a function; vector addition is commutative because the order in which vectors are added together does not affect the final sum
    component (of a 2-d vector) a piece of a vector that points in either the vertical or the horizontal direction; every 2-d vector can be expressed as a sum of two vertical and horizontal vector components
    direction (of a vector) the orientation of a vector in space
    head (of a vector) the end point of a vector; the location of the tip of the vector’s arrowhead; also referred to as the “tip”
    head-to-tail method a method of adding vectors in which the tail of each vector is placed at the head of the previous vector
    kinematics the study of motion without regard to mass or force
    magnitude (of a vector) the length or size of a vector; magnitude is a scalar quantity
    motion displacement of an object as a function of time
    projectile an object that travels through the air and experiences only acceleration due to gravity
    projectile motion the motion of an object that is subject only to the acceleration of gravity
    range the maximum horizontal distance that a projectile travels
    relative velocity the velocity of an object as observed from a particular reference frame
    relativity the study of how different observers moving relative to each other measure the same phenomenon
    resultant the sum of two or more vectors
    resultant vector the vector sum of two or more vectors
    scalar a quantity with magnitude but no direction
    tail the start point of a vector; opposite to the head or tip of the arrow
    trajectory the path of a projectile through the air
    vector a quantity that has both magnitude and direction; an arrow used to represent quantities with both magnitude and direction
    vector addition the rules that apply to adding vectors together
    velocity speed in a given direction
    carrier particle a fundamental particle of nature that is surrounded by a characteristic force field; photons are carrier particles of the electromagnetic force
    dynamics the study of how forces affect the motion of objects and systems
    external force a force acting on an object or system that originates outside of the object or system
    force a push or pull on an object with a specific magnitude and direction; can be represented by vectors; can be expressed as a multiple of a standard force
    force field a region in which a test particle will experience a force
    free-body diagram a sketch showing all of the external forces acting on an object or system; the system is represented by a dot, and the forces are represented by vectors extending outward from the dot
    free-fall a situation in which the only force acting on an object is the force due to gravity
    friction a force past each other of objects that are touching; examples include rough surfaces and air resistance
    inertia the tendency of an object to remain at rest or remain in motion
    inertial frame of reference a coordinate system that is not accelerating; all forces acting in an inertial frame of reference are real forces, as opposed to fictitious forces that are observed due to an accelerating frame of reference
    law of inertia see Newton’s first law of motion
    mass the quantity of matter in a substance; measured in kilograms
    net external force the vector sum of all external forces acting on an object or system; causes a mass to accelerate
    Newton’s first law of motion a body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force; also known as the law of inertia
    Newton’s second law of motion the net external force Fnet on an object with mass m is proportional to and in the same direction as the acceleration of the object, a, and inversely proportional to the mass; defined mathematically as a=Fnet/ m
    Newton’s third law of motion whenever one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that the first body exerts
    normal force the force that a surface applies to an object to support the weight of the object; acts perpendicular to the surface on which the object rests
    system defined by the boundaries of an object or collection of objects being observed; all forces originating from outside of the system are considered external forces
    tension the pulling force that acts along a medium, especially a stretched flexible connector, such as a rope or cable; when a rope supports the weight of an object, the force on the object due to the rope is called a tension force
    thrust a reaction force that pushes a body forward in response to a backward force; rockets, airplanes, and cars are pushed forward by a thrust reaction force
    tensile strength the breaking stress that will cause permanent deformation or fraction of a material
    angular velocity ω, the rate of change of the angle with which an object moves on a circular path
    arc length Δs, the distance traveled by an object along a circular path
    banked curve the curve in a road that is sloping in a manner that helps a vehicle negotiate the curve
    center of mass the point where the entire mass of an object can be thought to be concentrated
    centrifugal force a fictitious force that tends to throw an object off when the object is rotating in a non-inertial frame of reference
    centripetal acceleration the acceleration of an object moving in a circle, directed toward the center
    centripetal force any net force causing uniform circular motion
    Coriolis force the fictitious force causing the apparent deflection of moving objects when viewed in a rotating frame of reference
    fictitious force a force having no physical origin
    gravitational constant, G a proportionality factor used in the equation for Newton’s universal law of gravitation; it is a universal constant—that is, it is thought to be the same everywhere in the universe
    ideal angle the angle at which a car can turn safely on a steep curve, which is in proportion to the ideal speed
    ideal banking the sloping of a curve in a road, where the angle of the slope allows the vehicle to negotiate the curve at a certain speed without the aid of friction between the tires and the road; the net external force on the vehicle equals the horizontal centripetal force in the absence of friction
    ideal speed the maximum safe speed at which a vehicle can turn on a curve without the aid of friction between the tire and the road
    microgravity an environment in which the apparent net acceleration of a body is small compared with that produced by Earth at its surface
    Newton’s universal law of gravitation every particle in the universe attracts every other particle with a force along a line joining them; the force is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
    non-inertial frame of reference an accelerated frame of reference
    pit a tiny indentation on the spiral track moulded into the top of the polycarbonate layer of CD
    radians a unit of angle measurement
    radius of curvature radius of a circular path
    rotation angle

    the ratio of the arc length to the radius of curvature on a circular path: Δθ=Δs/r

    ultracentrifuge a centrifuge optimized for spinning a rotor at very high speeds
    uniform circular motion the motion of an object in a circular path at constant speed
    basal metabolic rate the total energy conversion rate of a person at rest
    chemical energy the energy in a substance stored in the bonds between atoms and molecules that can be released in a chemical reaction
    conservation of mechanical energy the rule that the sum of the kinetic energies and potential energies remains constant if only conservative forces act on and within a system
    conservative force a force that does the same work for any given initial and final configuration, regardless of the path followed
    efficiency a measure of the effectiveness of the input of energy to do work; useful energy or work divided by the total input of energy
    electrical energy the energy carried by a flow of charge
    energy the ability to do work
    fossil fuels oil, natural gas, and coal
    friction the force between surfaces that opposes one sliding on the other; friction changes mechanical energy into thermal energy
    gravitational potential energy the energy an object has due to its position in a gravitational field
    horsepower an older non-SI unit of power, with 1 hp=746 W
    joule SI unit of work and energy, equal to one newton-meter
    kilowatt-hour (kW⋅h) unit used primarily for electrical energy provided by electric utility companies
    kinetic energy the energy an object has by reason of its motion, equal to 1/2mv2 for the translational (i.e., non-rotational) motion of an object of mass m moving at speed v
    law of conservation of energy the general law that total energy is constant in any process; energy may change in form or be transferred from one system to another, but the total remains the same
    mechanical energy the sum of kinetic energy and potential energy
    metabolic rate the rate at which the body uses food energy to sustain life and to do different activities
    net work work done by the net force, or vector sum of all the forces/, acting on an object
    nonconservative force a force whose work depends on the path followed between the given initial and final configurations
    nuclear energy energy released by changes within atomic nuclei, such as the fusion of two light nuclei or the fission of a heavy nucleus
    potential energy energy due to position, shape, or configuration
    potential energy of a spring the stored energy of a spring as a function of its displacement; when Hooke’s law applies, it is given by the expression 1/2kx2 where x is the distance the spring is compressed or extended and k is the spring constant
    power the rate at which work is done
    radiant energy the energy carried by electromagnetic waves
    renewable forms of energy those sources that cannot be used up, such as water, wind, solar, and biomass
    thermal energy the energy within an object due to the random motion of its atoms and molecules that accounts for the object's temperature
    useful work work done on an external system
    watt (W) SI unit of power, with 1 W=1 J/s
    work the transfer of energy by a force that causes an object to be displaced; the product of the component of the force in the direction of the displacement and the magnitude of the displacement
    work-energy theorem the result, based on Newton’s laws, that the net work done on an object is equal to its change in kinetic energy
    change in momentum the difference between the final and initial momentum; the mass times the change in velocity
    conservation of momentum principle when the net external force is zero, the total momentum of the system is conserved or constant
    elastic collision a collision that also conserves internal kinetic energy
    impulse the average net external force times the time it acts; equal to the change in momentum
    inelastic collision a collision in which internal kinetic energy is not conserved
    internal kinetic energy the sum of the kinetic energies of the objects in a system
    isolated system a system in which the net external force is zero
    linear momentum the product of mass and velocity
    perfectly inelastic collision a collision in which the colliding objects stick together
    point masses structureless particles with no rotation or spin
    quark fundamental constituent of matter and an elementary particle
    second law of motion physical law that states that the net external force equals the change in momentum of a system divided by the time over which it changes
    center of gravity the point where the total weight of the body is assumed to be concentrated
    dynamic equilibrium a state of equilibrium in which the net external force and torque on a system moving with constant velocity are zero
    mechanical advantage the ratio of output to input forces for any simple machine
    neutral equilibrium a state of equilibrium that is independent of a system’s displacements from its original position
    perpendicular lever arm the shortest distance from the pivot point to the line along which F lies
    SI units of torque newton times meters, usually written as N·m
    stable equilibrium a system, when displaced, experiences a net force or torque in a direction opposite to the direction of the displacement
    static equilibrium a state of equilibrium in which the net external force and torque acting on a system is zero
    static equilibrium equilibrium in which the acceleration of the system is zero and accelerated rotation does not occur
    torque turning or twisting effectiveness of a force
    unstable equilibrium a system, when displaced, experiences a net force or torque in the same direction as the displacement from equilibrium
    angular acceleration the rate of change of angular velocity with time
    angular momentum the product of moment of inertia and angular velocity
    change in angular velocity the difference between final and initial values of angular velocity
    kinematics of rotational motion describes the relationships among rotation angle, angular velocity, angular acceleration, and time
    law of conservation of angular momentum angular momentum is conserved, i.e., the initial angular momentum is equal to the final angular momentum when no external torque is applied to the system
    moment of inertia mass times the square of perpendicular distance from the rotation axis; for a point mass, it is I=mr2 and, because any object can be built up from a collection of point masses, this relationship is the basis for all other moments of inertia
    right-hand rule direction of angular velocity ω and angular momentum L in which the thumb of your right hand points when you curl your fingers in the direction of the disk’s rotation
    rotational inertia resistance to change of rotation. The more rotational inertia an object has, the harder it is to rotate
    rotational kinetic energy the kinetic energy due to the rotation of an object. This is part of its total kinetic energy
    tangential acceleration the acceleration in a direction tangent to the circle at the point of interest in circular motion
    torque the turning effectiveness of a force
    work-energy theorem if one or more external forces act upon a rigid object, causing its kinetic energy to change from KE1 to KE2 then the work W done by the net force is equal to the change in kinetic energy
    absolute pressure the sum of gauge pressure and atmospheric pressure
    adhesive forces the attractive forces between molecules of different types
    Archimedes’ principle the buoyant force on an object equals the weight of the fluid it displaces
    buoyant force the net upward force on any object in any fluid
    capillary action the tendency of a fluid to be raised or lowered in a narrow tube
    cohesive forces the attractive forces between molecules of the same type
    contact angle the angle θ between the tangent to the liquid surface and the surface
    density the mass per unit volume of a substance or object
    diastolic pressure the minimum blood pressure in the artery
    diastolic pressure minimum arterial blood pressure; indicator for the fluid balance
    fluids liquids and gases; a fluid is a state of matter that yields to shearing forces
    gauge pressure the pressure relative to atmospheric pressure
    glaucoma condition caused by the buildup of fluid pressure in the eye
    intraocular pressure fluid pressure in the eye
    micturition reflex stimulates the feeling of needing to urinate, triggered by bladder pressure
    Pascal’s Principle a change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container
    pressure the force per unit area perpendicular to the force, over which the force acts
    pressure the weight of the fluid divided by the area supporting it
    specific gravity the ratio of the density of an object to a fluid (usually water)
    surface tension the cohesive forces between molecules which cause the surface of a liquid to contract to the smallest possible surface area
    systolic pressure the maximum blood pressure in the artery
    systolic pressure maximum arterial blood pressure; indicator for the blood flow
    active transport the process in which a living membrane expends energy to move substances across
    Bernoulli’s equation the equation resulting from applying conservation of energy to an incompressible frictionless fluid: P + 1/2pv2 + pgh = constant , through the fluid
    Bernoulli’s principle Bernoulli’s equation applied at constant depth: P1 + 1/2pv12 = P2 + 1/2pv22
    dialysis the transport of any molecule other than water through a semipermeable membrane from a region of high concentration to one of low concentration
    diffusion the movement of substances due to random thermal molecular motion
    flow rate abbreviated Q, it is the volume V that flows past a particular point during a time t, or Q = V/t
    fluid dynamics the physics of fluids in motion
    laminar a type of fluid flow in which layers do not mix
    liter a unit of volume, equal to 10−3 m3
    osmosis the transport of water through a semipermeable membrane from a region of high concentration to one of low concentration
    osmotic pressure the back pressure which stops the osmotic process if one solution is pure water
    Poiseuille’s law the rate of laminar flow of an incompressible fluid in a tube: Q = (P2P1)πr4/8ηl
    Poiseuille’s law for resistance the resistance to laminar flow of an incompressible fluid in a tube: R = 8ηl/πr4
    relative osmotic pressure the back pressure which stops the osmotic process if neither solution is pure water
    reverse dialysis the process that occurs when back pressure is sufficient to reverse the normal direction of dialysis through membranes
    reverse osmosis the process that occurs when back pressure is sufficient to reverse the normal direction of osmosis through membranes
    Reynolds number a dimensionless parameter that can reveal whether a particular flow is laminar or turbulent
    semipermeable a type of membrane that allows only certain small molecules to pass through
    terminal speed the speed at which the viscous drag of an object falling in a viscous fluid is equal to the other forces acting on the object (such as gravity), so that the acceleration of the object is zero
    turbulence fluid flow in which layers mix together via eddies and swirls
    viscosity the friction in a fluid, defined in terms of the friction between layers
    viscous drag a resistance force exerted on a moving object, with a nontrivial dependence on velocity
    absolute zero the lowest possible temperature; the temperature at which all molecular motion ceases
    Avogadro’s number NA , the number of molecules or atoms in one mole of a substance; NA=6.02×1023 particles/mole
    Boltzmann constant k , a physical constant that relates energy to temperature; k=1.38×10–23 J/K
    Celsius scale temperature scale in which the freezing point of water is 0 ºC and the boiling point of water is 100 ºC
    coefficient of linear expansion α, the change in length, per unit length, per 1ºC change in temperature; a constant used in the calculation of linear expansion; the coefficient of linear expansion depends on the material and to some degree on the temperature of the material
    coefficient of volume expansion β, the change in volume, per unit volume, per 1ºC change in temperature
    critical point the temperature above which a liquid cannot exist
    critical pressure the minimum pressure needed for a liquid to exist at the critical temperature
    critical temperature the temperature above which a liquid cannot exist
    Dalton’s law of partial pressures the physical law that states that the total pressure of a gas is the sum of partial pressures of the component gases
    degree Celsius unit on the Celsius temperature scale
    degree Fahrenheit unit on the Fahrenheit temperature scale
    dew point the temperature at which relative humidity is 100%; the temperature at which water starts to condense out of the air
    Fahrenheit scale temperature scale in which the freezing point of water is 32 ºF and the boiling point of water is 212 ºF
    ideal gas law the physical law that relates the pressure and volume of a gas to the number of gas molecules or number of moles of gas and the temperature of the gas
    Kelvin scale temperature scale in which 0 K is the lowest possible temperature, representing absolute zero
    mole the quantity of a substance whose mass (in grams) is equal to its molecular mass
    partial pressure the pressure a gas would create if it occupied the total volume of space available
    percent relative humidity the ratio of vapor density to saturation vapor density
    phase diagram a graph of pressure vs. temperature of a particular substance, showing at which pressures and temperatures the three phases of the substance occur
    PV diagram a graph of pressure vs. volume
    relative humidity the amount of water in the air relative to the maximum amount the air can hold
    saturation the condition of 100% relative humidity
    sublimation the phase change from solid to gas
    temperature the quantity measured by a thermometer
    thermal energy the average translational kinetic energy of a molecule
    thermal equilibrium the condition in which heat no longer flows between two objects that are in contact; the two objects have the same temperature
    thermal expansion the change in size or volume of an object with change in temperature
    thermal stress stress caused by thermal expansion or contraction
    triple point the pressure and temperature at which a substance exists in equilibrium as a solid, liquid, and gas
    vapor a gas at a temperature below the boiling temperature
    vapor pressure the pressure at which a gas coexists with its solid or liquid phase
    zeroth law of thermodynamics law that states that if two objects are in thermal equilibrium, and a third object is in thermal equilibrium with one of those objects, it is also in thermal equilibrium with the other object
    conduction heat transfer through stationary matter by physical contact
    convection heat transfer by the macroscopic movement of fluid
    emissivity measure of how well an object radiates
    greenhouse effect warming of the Earth that is due to gases such as carbon dioxide and methane that absorb infrared radiation from the Earth’s surface and reradiate it in all directions, thus sending a fraction of it back toward the surface of the Earth
    heat the spontaneous transfer of energy due to a temperature difference
    heat of sublimation the energy required to change a substance from the solid phase to the vapor phase
    kilocalorie 1kilocalorie=1000caloriessize 12{1`"kilocalorie=1000"`"calories"} {}
    latent heat coefficient a physical constant equal to the amount of heat transferred for every 1 kg of a substance during the change in phase of the substance
    mechanical equivalent of heat the work needed to produce the same effects as heat transfer
    net rate of heat transfer by radiation is Qnett=σeA(T42−T41)
    R factor the ratio of thickness to the conductivity of a material
    radiation heat transfer which occurs when microwaves, infrared radiation, visible light, or other electromagnetic radiation is emitted or absorbed
    radiation energy transferred by electromagnetic waves directly as a result of a temperature difference
    rate of conductive heat transfer rate of heat transfer from one material to another
    specific heat the amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 ºC
    Stefan-Boltzmann law of radiation Qt=σeAT4, where σ is the Stefan-Boltzmann constant, A is the surface area of the object, T is the absolute temperature, and e is the emissivity
    sublimation the transition from the solid phase to the vapor phase
    thermal conductivity the property of a material’s ability to conduct heat
    adiabatic process a process in which no heat transfer takes place
    Carnot cycle a cyclical process that uses only reversible processes, the adiabatic and isothermal processes
    Carnot efficiency the maximum theoretical efficiency for a heat engine
    Carnot engine a heat engine that uses a Carnot cycle
    change in entropy the ratio of heat transfer to temperature Q/T
    coefficient of performance for a heat pump, it is the ratio of heat transfer at the output (the hot reservoir) to the work supplied; for a refrigerator or air conditioner, it is the ratio of heat transfer from the cold reservoir to the work supplied
    cyclical process a process in which the path returns to its original state at the end of every cycle
    entropy a measurement of a system's disorder and its inability to do work in a system
    first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system
    heat engine a machine that uses heat transfer to do work
    heat pump a machine that generates heat transfer from cold to hot
    human metabolism conversion of food into heat transfer, work, and stored fat
    internal energy the sum of the kinetic and potential energies of a system’s atoms and molecules
    irreversible process any process that depends on path direction
    isobaric process constant-pressure process in which a gas does work
    isochoric process a constant-volume process
    isothermal process a constant-temperature process
    macrostate an overall property of a system
    microstate each sequence within a larger macrostate
    Otto cycle a thermodynamic cycle, consisting of a pair of adiabatic processes and a pair of isochoric processes, that converts heat into work, e.g., the four-stroke engine cycle of intake, compression, ignition, and exhaust
    reversible process a process in which both the heat engine system and the external environment theoretically can be returned to their original states
    second law of thermodynamics heat transfer flows from a hotter to a cooler object, never the reverse, and some heat energy in any process is lost to available work in a cyclical process
    second law of thermodynamics stated in terms of entropy the total entropy of a system either increases or remains constant; it never decreases
    statistical analysis using statistics to examine data, such as counting microstates and macrostates
    amplitude the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position
    antinode the location of maximum amplitude in standing waves
    beat frequency the frequency of the amplitude fluctuations of a wave
    constructive interference when two waves arrive at the same point exactly in phase; that is, the crests of the two waves are precisely aligned, as are the troughs
    critical damping the condition in which the damping of an oscillator causes it to return as quickly as possible to its equilibrium position without oscillating back and forth about this position
    deformation displacement from equilibrium
    destructive interference when two identical waves arrive at the same point exactly out of phase; that is, precisely aligned crest to trough
    elastic potential energy potential energy stored as a result of deformation of an elastic object, such as the stretching of a spring
    force constant a constant related to the rigidity of a system: the larger the force constant, the more rigid the system; the force constant is represented by k
    frequency number of events per unit of time
    fundamental frequency the lowest frequency of a periodic waveform
    intensity power per unit area
    longitudinal wave a wave in which the disturbance is parallel to the direction of propagation
    natural frequency the frequency at which a system would oscillate if there were no driving and no damping forces
    nodes the points where the string does not move; more generally, nodes are where the wave disturbance is zero in a standing wave
    oscillate moving back and forth regularly between two points
    over damping the condition in which damping of an oscillator causes it to return to equilibrium without oscillating; oscillator moves more slowly toward equilibrium than in the critically damped system
    overtones multiples of the fundamental frequency of a sound
    period time it takes to complete one oscillation
    periodic motion motion that repeats itself at regular time intervals
    resonance the phenomenon of driving a system with a frequency equal to the system's natural frequency
    resonate a system being driven at its natural frequency
    restoring force force acting in opposition to the force caused by a deformation
    simple harmonic motion the oscillatory motion in a system where the net force can be described by Hooke’s law
    simple harmonic oscillator a device that implements Hooke’s law, such as a mass that is attached to a spring, with the other end of the spring being connected to a rigid support such as a wall
    simple pendulum an object with a small mass suspended from a light wire or string
    superposition the phenomenon that occurs when two or more waves arrive at the same point
    transverse wave a wave in which the disturbance is perpendicular to the direction of propagation
    under damping the condition in which damping of an oscillator causes it to return to equilibrium with the amplitude gradually decreasing to zero; system returns to equilibrium faster but overshoots and crosses the equilibrium position one or more times
    wave a disturbance that moves from its source and carries energy
    wave velocity the speed at which the disturbance moves. Also called the propagation velocity or propagation speed
    wavelength the distance between adjacent identical parts of a wave
    acoustic impedance property of medium that makes the propagation of sound waves more difficult
    antinode point of maximum displacement
    bow wake V-shaped disturbance created when the wave source moves faster than the wave propagation speed
    Doppler effect an alteration in the observed frequency of a sound due to motion of either the source or the observer
    Doppler shift the actual change in frequency due to relative motion of source and observer
    Doppler-shifted ultrasound a medical technique to detect motion and determine velocity through the Doppler shift of an echo
    fundamental the lowest-frequency resonance
    harmonics the term used to refer collectively to the fundamental and its overtones
    hearing the perception of sound
    infrasound sounds below 20 Hz
    intensity the power per unit area carried by a wave
    intensity reflection coefficient a measure of the ratio of the intensity of the wave reflected off a boundary between two media relative to the intensity of the incident wave
    loudness the perception of sound intensity
    node point of zero displacement
    note basic unit of music with specific names, combined to generate tunes
    overtones all resonant frequencies higher than the fundamental
    phon the numerical unit of loudness
    pitch the perception of the frequency of a sound
    sonic boom a constructive interference of sound created by an object moving faster than sound
    sound a disturbance of matter that is transmitted from its source outward
    sound intensity level a unitless quantity telling you the level of the sound relative to a fixed standard
    sound pressure level the ratio of the pressure amplitude to a reference pressure
    timbre number and relative intensity of multiple sound frequencies
    tone number and relative intensity of multiple sound frequencies
    ultrasound sounds above 20,000 Hz
    conductor a material that allows electrons to move separately from their atomic orbits
    conductor an object with properties that allow charges to move about freely within it
    Coulomb force another term for the electrostatic force
    Coulomb interaction the interaction between two charged particles generated by the Coulomb forces they exert on one another
    Coulomb’s law the mathematical equation calculating the electrostatic force vector between two charged particles
    dipole a molecule’s lack of symmetrical charge distribution, causing one side to be more positive and another to be more negative
    electric charge a physical property of an object that causes it to be attracted toward or repelled from another charged object; each charged object generates and is influenced by a force called an electromagnetic force
    electric field a three-dimensional map of the electric force extended out into space from a point charge
    electric field lines a series of lines drawn from a point charge representing the magnitude and direction of force exerted by that charge
    electromagnetic force one of the four fundamental forces of nature; the electromagnetic force consists of static electricity, moving electricity and magnetism
    electron a particle orbiting the nucleus of an atom and carrying the smallest unit of negative charge
    electrostatic equilibrium an electrostatically balanced state in which all free electrical charges have stopped moving about
    electrostatic force the amount and direction of attraction or repulsion between two charged bodies
    electrostatic precipitators filters that apply charges to particles in the air, then attract those charges to a filter, removing them from the airstream
    electrostatic repulsion the phenomenon of two objects with like charges repelling each other
    electrostatics the study of electric forces that are static or slow-moving
    Faraday cage a metal shield which prevents electric charge from penetrating its surface
    field a map of the amount and direction of a force acting on other objects, extending out into space
    free charge an electrical charge (either positive or negative) which can move about separately from its base molecule
    free electron an electron that is free to move away from its atomic orbit
    grounded when a conductor is connected to the Earth, allowing charge to freely flow to and from Earth’s unlimited reservoir
    grounded connected to the ground with a conductor, so that charge flows freely to and from the Earth to the grounded object
    induction the process by which an electrically charged object brought near a neutral object creates a charge in that object
    ink-jet printer small ink droplets sprayed with an electric charge are controlled by electrostatic plates to create images on paper
    insulator a material that holds electrons securely within their atomic orbits
    ionosphere a layer of charged particles located around 100 km above the surface of Earth, which is responsible for a range of phenomena including the electric field surrounding Earth
    laser printer uses a laser to create a photoconductive image on a drum, which attracts dry ink particles that are then rolled onto a sheet of paper to print a high-quality copy of the image
    law of conservation of charge states that whenever a charge is created, an equal amount of charge with the opposite sign is created simultaneously
    photoconductor a substance that is an insulator until it is exposed to light, when it becomes a conductor
    point charge A charged particle, designated Qsize 12{Q} {}, generating an electric field
    polar molecule a molecule with an asymmetrical distribution of positive and negative charge
    polarization slight shifting of positive and negative charges to opposite sides of an atom or molecule
    polarized a state in which the positive and negative charges within an object have collected in separate locations
    proton a particle in the nucleus of an atom and carrying a positive charge equal in magnitude and opposite in sign to the amount of negative charge carried by an electron
    screening the dilution or blocking of an electrostatic force on a charged object by the presence of other charges nearby
    static electricity a buildup of electric charge on the surface of an object
    test charge A particle (designated qsize 12{q} {}) with either a positive or negative charge set down within an electric field generated by a point charge
    Van de Graaff generator a machine that produces a large amount of excess charge, used for experiments with high voltage
    vector a quantity with both magnitude and direction
    vector addition mathematical combination of two or more vectors, including their magnitudes, directions, and positions
    xerography a dry copying process based on electrostatics
    capacitance amount of charge stored per unit volt
    capacitor a device that stores electric charge
    defibrillator a machine used to provide an electrical shock to a heart attack victim's heart in order to restore the heart's normal rhythmic pattern
    dielectric an insulating material
    dielectric strength the maximum electric field above which an insulating material begins to break down and conduct
    electric potential potential energy per unit charge
    electron volt the energy given to a fundamental charge accelerated through a potential difference of one volt
    equipotential line a line along which the electric potential is constant
    grounding fixing a conductor at zero volts by connecting it to the earth or ground
    mechanical energy sum of the kinetic energy and potential energy of a system; this sum is a constant
    parallel plate capacitor two identical conducting plates separated by a distance
    polar molecule a molecule with inherent separation of charge
    potential difference (or voltage) change in potential energy of a charge moved from one point to another, divided by the charge; units of potential difference are joules per coulomb, known as volt
    scalar physical quantity with magnitude but no direction
    vector physical quantity with both magnitude and direction
    AC current current that fluctuates sinusoidally with time, expressed as I = I0 sin 2πft, where I is the current at time t, I0 is the peak current, and f is the frequency in hertz
    AC voltage voltage that fluctuates sinusoidally with time, expressed as V = V0 sin 2πft, where V is the voltage at time t, V0 is the peak voltage, and f is the frequency in hertz
    alternating current (AC) the flow of electric charge that periodically reverses direction
    ampere (amp) the SI unit for current; 1 A = 1 C/s
    bioelectricity electrical effects in and created by biological systems
    direct current (DC) the flow of electric charge in only one direction
    drift velocity the average velocity at which free charges flow in response to an electric field
    electric current the rate at which charge flows, I = ΔQt
    electric power the rate at which electrical energy is supplied by a source or dissipated by a device; it is the product of current times voltage
    electrocardiogram (ECG) usually abbreviated ECG, a record of voltages created by depolarization and repolarization, especially in the heart
    microshock sensitive a condition in which a person’s skin resistance is bypassed, possibly by a medical procedure, rendering the person vulnerable to electrical shock at currents about 1/1000 the normally required level
    nerve conduction the transport of electrical signals by nerve cells
    ohm the unit of resistance, given by 1Ω = 1 V/A
    Ohm’s law an empirical relation stating that the current I is proportional to the potential difference V, ∝ V; it is often written as I = V/R, where R is the resistance
    ohmic a type of a material for which Ohm's law is valid
    resistance the electric property that impedes current; for ohmic materials, it is the ratio of voltage to current, R = V/I
    resistivity an intrinsic property of a material, independent of its shape or size, directly proportional to the resistance, denoted by ρ
    rms current the root mean square of the current, Irms=I0/2–√size 12{I rSub { size 8{"rms "} } = I rSub { size 8{0} } / sqrt {2} } {} , where I0 is the peak current, in an AC system
    rms voltage the root mean square of the voltage, Vrms=V0/2–√size 12{V rSub { size 8{"rms "} } = V rSub { size 8{0} } / sqrt {2} } {} , where V0 is the peak voltage, in an AC system
    semipermeable property of a membrane that allows only certain types of ions to cross it
    shock hazard when electric current passes through a person
    short circuit also known as a “short,” a low-resistance path between terminals of a voltage source
    simple circuit a circuit with a single voltage source and a single resistor
    temperature coefficient of resistivity an empirical quantity, denoted by α, which describes the change in resistance or resistivity of a material with temperature
    thermal hazard a hazard in which electric current causes undesired thermal effects
    ammeter an instrument that measures current
    analog meter a measuring instrument that gives a readout in the form of a needle movement over a marked gauge
    bridge device a device that forms a bridge between two branches of a circuit; some bridge devices are used to make null measurements in circuits
    capacitance the maximum amount of electric potential energy that can be stored (or separated) for a given electric potential
    capacitor an electrical component used to store energy by separating electric charge on two opposing plates
    conservation laws require that energy and charge be conserved in a system
    current the flow of charge through an electric circuit past a given point of measurement
    current sensitivity the maximum current that a galvanometer can read
    digital meter a measuring instrument that gives a readout in a digital form
    electromotive force (emf) the potential difference of a source of electricity when no current is flowing; measured in volts
    full-scale deflection the maximum deflection of a galvanometer needle, also known as current sensitivity; a galvanometer with a full-scale deflection of 50 μAsize 12{"50" mA} {} has a maximum deflection of its needle when 50 μAsize 12{"50" μA} {} flows through it
    galvanometer an analog measuring device, denoted by G, that measures current flow using a needle deflection caused by a magnetic field force acting upon a current-carrying wire
    internal resistance the amount of resistance within the voltage source
    Joule’s law the relationship between potential electrical power, voltage, and resistance in an electrical circuit, given by: Pe=IVsize 12{P rSub { size 8{e} } = ital "IV"} {}
    junction rule Kirchhoff’s first rule, which applies the conservation of charge to a junction; current is the flow of charge; thus, whatever charge flows into the junction must flow out; the rule can be stated I1=I2+I3size 12{I rSub { size 8{1} } =I rSub { size 8{2} } +I rSub { size 8{3} } } {}
    Kirchhoff’s rules a set of two rules, based on conservation of charge and energy, governing current and changes in potential in an electric circuit
    loop rule Kirchhoff’s second rule, which states that in a closed loop, whatever energy is supplied by emf must be transferred into other forms by devices in the loop, since there are no other ways in which energy can be transferred into or out of the circuit. Thus, the emf equals the sum of the IRsize 12{ ital "IR"} {} (voltage) drops in the loop and can be stated: emf=Ir+IR1+IR2size 12{"emf"= ital "Ir"+ ital "IR" rSub { size 8{1} } + ital "IR" rSub { size 8{2} } } {}
    null measurements methods of measuring current and voltage more accurately by balancing the circuit so that no current flows through the measurement device
    Ohm’s law the relationship between current, voltage, and resistance within an electrical circuit: V=IRsize 12{V= ital "IR"} {}
    ohmmeter an instrument that applies a voltage to a resistance, measures the current, calculates the resistance using Ohm’s law, and provides a readout of this calculated resistance
    parallel the wiring of resistors or other components in an electrical circuit such that each component receives an equal voltage from the power source; often pictured in a ladder-shaped diagram, with each component on a rung of the ladder
    potential difference the difference in electric potential between two points in an electric circuit, measured in volts
    potentiometer a null measurement device for measuring potentials (voltages)
    RC circuit a circuit that contains both a resistor and a capacitor
    resistance causing a loss of electrical power in a circuit
    resistor a component that provides resistance to the current flowing through an electrical circuit
    series a sequence of resistors or other components wired into a circuit one after the other
    shunt resistance a small resistance Rsize 12{R} {} placed in parallel with a galvanometer G to produce an ammeter; the larger the current to be measured, the smaller Rsize 12{R} {} must be; most of the current flowing through the meter is shunted through Rsize 12{R} {} to protect the galvanometer
    terminal voltage the voltage measured across the terminals of a source of potential difference
    voltage the electrical potential energy per unit charge; electric pressure created by a power source, such as a battery
    voltage drop the loss of electrical power as a current travels through a resistor, wire or other component
    voltmeter an instrument that measures voltage
    Wheatstone bridge a null measurement device for calculating resistance by balancing potential drops in a circuit
    Ampere’s law the physical law that states that the magnetic field around an electric current is proportional to the current; each segment of current produces a magnetic field like that of a long straight wire, and the total field of any shape current is the vector sum of the fields due to each segment
    B-field another term for magnetic field
    Biot-Savart law a physical law that describes the magnetic field generated by an electric current in terms of a specific equation
    Curie temperature the temperature above which a ferromagnetic material cannot be magnetized
    direction of magnetic field lines the direction that the north end of a compass needle points
    domains regions within a material that behave like small bar magnets
    electromagnet an object that is temporarily magnetic when an electrical current is passed through it
    electromagnetism the use of electrical currents to induce magnetism
    ferromagnetic materials, such as iron, cobalt, nickel, and gadolinium, that exhibit strong magnetic effects
    gauss G, the unit of the magnetic field strength; 1 G=10–4Tsize 12{"1 G"="10" rSup { size 8{ - 4} } `T} {}
    Hall effect the creation of voltage across a current-carrying conductor by a magnetic field
    Hall emf the electromotive force created by a current-carrying conductor by a magnetic field, ε=Blvsize 12{ε= ital "Blv"} {}
    Lorentz force the force on a charge moving in a magnetic field
    magnetic field the representation of magnetic forces
    magnetic field lines the pictorial representation of the strength and the direction of a magnetic field
    magnetic field strength (magnitude) produced by a long straight current-carrying wire defined as B=μ0I2πr, where I is the current, r is the shortest distance to the wire, and μ0 is the permeability of free space
    magnetic field strength at the center of a circular loop defined as B=μ0I2R where R is the radius of the loop
    magnetic field strength inside a solenoid defined as B=μ0nI where n is the number of loops per unit length of the solenoid (n=N/l, with N being the number of loops and l the length)
    magnetic force the force on a charge produced by its motion through a magnetic field; the Lorentz force
    magnetic monopoles an isolated magnetic pole; a south pole without a north pole, or vice versa (no magnetic monopole has ever been observed)
    magnetic resonance imaging (MRI) a medical imaging technique that uses magnetic fields create detailed images of internal tissues and organs
    magnetized to be turned into a magnet; to be induced to be magnetic
    magnetocardiogram (MCG) a recording of the heart’s magnetic field as it beats
    magnetoencephalogram (MEG) a measurement of the brain’s magnetic field
    Maxwell’s equations a set of four equations that describe electromagnetic phenomena
    meter common application of magnetic torque on a current-carrying loop that is very similar in construction to a motor; by design, the torque is proportional to I and not θ, so the needle deflection is proportional to the current
    motor loop of wire in a magnetic field; when current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft; electrical energy is converted to mechanical work in the process
    north magnetic pole the end or the side of a magnet that is attracted toward Earth’s geographic north pole
    nuclear magnetic resonance (NMR) a phenomenon in which an externally applied magnetic field interacts with the nuclei of certain atoms
    permeability of free space the measure of the ability of a material, in this case free space, to support a magnetic field; the constant μ0=4π×10−7T⋅m/A
    right hand rule 1 (RHR-1) the rule to determine the direction of the magnetic force on a positive moving charge: when the thumb of the right hand points in the direction of the charge’s velocity vsize 12{v} {} and the fingers point in the direction of the magnetic field Bsize 12{B} {}, then the force on the charge is perpendicular and away from the palm; the force on a negative charge is perpendicular and into the palm
    right hand rule 2 (RHR-2) a rule to determine the direction of the magnetic field induced by a current-carrying wire: Point the thumb of the right hand in the direction of current, and the fingers curl in the direction of the magnetic field loops
    solenoid a thin wire wound into a coil that produces a magnetic field when an electric current is passed through it
    south magnetic pole the end or the side of a magnet that is attracted toward Earth’s geographic south pole
    tesla T, the SI unit of the magnetic field strength; 1 T=1 NA⋅m
    back emf the emf generated by a running motor, because it consists of a coil turning in a magnetic field; it opposes the voltage powering the motor
    capacitive reactance the opposition of a capacitor to a change in current; calculated by XC=1/2πfC
    characteristic time constant denoted by τ, of a particular series RL circuit is calculated by τ=L/R, where L is the inductance and R is the resistance
    eddy current a current loop in a conductor caused by motional emf
    electric generator a device for converting mechanical work into electric energy; it induces an emf by rotating a coil in a magnetic field
    electromagnetic induction the process of inducing an emf (voltage) with a change in magnetic flux
    emf induced in a generator coil emf=NABω sin ωt, where A is the area of an N-turn coil rotated at a constant angular velocity ω in a uniform magnetic field B, over a period of time t
    energy stored in an inductor self-explanatory; calculated by Eind=1/2LI2
    Faraday’s law of induction the means of calculating the emf in a coil due to changing magnetic flux, given by emf=−NΔΦΔt
    henry the unit of inductance; 1H=1Ω⋅s
    impedance the AC analogue to resistance in a DC circuit; it is the combined effect of resistance, inductive reactance, and capacitive reactance in the form Z=R2+(XL−XC)2−−−−−−−−−−−−−√
    inductance a property of a device describing how efficient it is at inducing emf in another device
    induction (magnetic induction) the creation of emfs and hence currents by magnetic fields
    inductive reactance the opposition of an inductor to a change in current; calculated by XL=2πfL
    inductor a device that exhibits significant self-inductance
    Lenz’s law the minus sign in Faraday’s law, signifying that the emf induced in a coil opposes the change in magnetic flux
    magnetic damping the drag produced by eddy currents
    magnetic flux the amount of magnetic field going through a particular area, calculated with Φ=BAcosθ where Bis the magnetic field strength over an area A at an angle θ with the perpendicular to the area
    mutual inductance how effective a pair of devices are at inducing emfs in each other
    peak emf emf0=NABω
    phase angle denoted by ϕ, the amount by which the voltage and current are out of phase with each other in a circuit
    power factor the amount by which the power delivered in the circuit is less than the theoretical maximum of the circuit due to voltage and current being out of phase; calculated by cosϕ
    resonant frequency the frequency at which the impedance in a circuit is at a minimum, and also the frequency at which the circuit would oscillate if not driven by a voltage source; calculated by f0=1/2πLC√
    self-inductance how effective a device is at inducing emf in itself
    shock hazard the term for electrical hazards due to current passing through a human
    step-down transformer a transformer that decreases voltage
    step-up transformer a transformer that increases voltage
    thermal hazard the term for electrical hazards due to overheating
    three-wire system the wiring system used at present for safety reasons, with live, neutral, and ground wires
    transformer a device that transforms voltages from one value to another using induction
    transformer equation the equation showing that the ratio of the secondary to primary voltages in a transformer equals the ratio of the number of loops in their coils; VsVp=NsNp
    amplitude the height, or magnitude, of an electromagnetic wave
    amplitude modulation (AM) a method for placing information on electromagnetic waves by modulating the amplitude of a carrier wave with an audio signal, resulting in a wave with constant frequency but varying amplitude
    carrier wave an electromagnetic wave that carries a signal by modulation of its amplitude or frequency
    electric field a vector quantity (E); the lines of electric force per unit charge, moving radially outward from a positive charge and in toward a negative charge
    electric field lines a pattern of imaginary lines that extend between an electric source and charged objects in the surrounding area, with arrows pointed away from positively charged objects and toward negatively charged objects. The more lines in the pattern, the stronger the electric field in that region
    electric field strength the magnitude of the electric field, denoted E-field
    electromagnetic spectrum the full range of wavelengths or frequencies of electromagnetic radiation
    electromagnetic waves radiation in the form of waves of electric and magnetic energy
    electromotive force (emf) energy produced per unit charge, drawn from a source that produces an electrical current
    extremely low frequency (ELF) electromagnetic radiation with wavelengths usually in the range of 0 to 300 Hz, but also about 1kHz
    frequency the number of complete wave cycles (up-down-up) passing a given point within one second (cycles/second)
    frequency modulation (FM) a method of placing information on electromagnetic waves by modulating the frequency of a carrier wave with an audio signal, producing a wave of constant amplitude but varying frequency
    gamma ray (γ-ray); extremely high frequency electromagnetic radiation emitted by the nucleus of an atom, either from natural nuclear decay or induced nuclear processes in nuclear reactors and weapons. The lower end of the γ-ray frequency range overlaps the upper end of the X-ray range, but γ rays can have the highest frequency of any electromagnetic radiation
    hertz an SI unit denoting the frequency of an electromagnetic wave, in cycles per second
    infrared radiation (IR) a region of the electromagnetic spectrum with a frequency range that extends from just below the red region of the visible light spectrum up to the microwave region, or from 0.74μm to 300 μm
    intensity the power of an electric or magnetic field per unit area, for example, Watts per square meter
    magnetic field a vector quantity (B); can be used to determine the magnetic force on a moving charged particle
    magnetic field lines a pattern of continuous, imaginary lines that emerge from and enter into opposite magnetic poles. The density of the lines indicates the magnitude of the magnetic field
    magnetic field strength the magnitude of the magnetic field, denoted B-field
    maximum field strength the maximum amplitude an electromagnetic wave can reach, representing the maximum amount of electric force and/or magnetic flux that the wave can exert
    Maxwell’s equations a set of four equations that comprise a complete, overarching theory of electromagnetism
    microwaves electromagnetic waves with wavelengths in the range from 1 mm to 1 m; they can be produced by currents in macroscopic circuits and devices
    oscillate to fluctuate back and forth in a steady beat
    radar a common application of microwaves. Radar can determine the distance to objects as diverse as clouds and aircraft, as well as determine the speed of a car or the intensity of a rainstorm
    radio waves electromagnetic waves with wavelengths in the range from 1 mm to 100 km; they are produced by currents in wires and circuits and by astronomical phenomena
    resonant a system that displays enhanced oscillation when subjected to a periodic disturbance of the same frequency as its natural frequency
    RLC circuit an electric circuit that includes a resistor, capacitor and inductor
    speed of light in a vacuum, such as space, the speed of light is a constant 3 x 108 m/s
    standing wave a wave that oscillates in place, with nodes where no motion happens
    thermal agitation the thermal motion of atoms and molecules in any object at a temperature above absolute zero, which causes them to emit and absorb radiation
    transverse wave a wave, such as an electromagnetic wave, which oscillates perpendicular to the axis along the line of travel
    TV video and audio signals broadcast on electromagnetic waves
    ultra-high frequency (UHF) TV channels in an even higher frequency range than VHF, of 470 to 1000 MHz
    ultraviolet radiation (UV) electromagnetic radiation in the range extending upward in frequency from violet light and overlapping with the lowest X-ray frequencies, with wavelengths from 400 nm down to about 10 nm
    very high frequency (VHF) TV channels utilizing frequencies in the two ranges of 54 to 88 MHz and 174 to 222 MHz
    visible light the narrow segment of the electromagnetic spectrum to which the normal human eye responds
    wavelength the distance from one peak to the next in a wave
    X-ray invisible, penetrating form of very high frequency electromagnetic radiation, overlapping both the ultraviolet range and the γsize 12{g} {}-ray range
    converging lens a convex lens in which light rays that enter it parallel to its axis converge at a single point on the opposite side
    converging mirror a concave mirror in which light rays that strike it parallel to its axis converge at one or more points along the axis
    corner reflector an object consisting of two mutually perpendicular reflecting surfaces, so that the light that enters is reflected back exactly parallel to the direction from which it came
    critical angle incident angle that produces an angle of refraction of 90ºsize 12{"90"°} {}
    dispersion spreading of white light into its full spectrum of wavelengths
    diverging lens a concave lens in which light rays that enter it parallel to its axis bend away (diverge) from its axis
    diverging mirror a convex mirror in which light rays that strike it parallel to its axis bend away (diverge) from its axis
    fiber optics transmission of light down fibers of plastic or glass, applying the principle of total internal reflection
    focal length distance from the center of a lens or curved mirror to its focal point
    focal point for a converging lens or mirror, the point at which converging light rays cross; for a diverging lens or mirror, the point from which diverging light rays appear to originate
    geometric optics part of optics dealing with the ray aspect of light
    index of refraction for a material, the ratio of the speed of light in vacuum to that in the material
    law of reflection angle of reflection equals the angle of incidence
    law of reflection angle of reflection equals the angle of incidence
    magnification ratio of image height to object height
    mirror smooth surface that reflects light at specific angles, forming an image of the person or object in front of it
    power inverse of focal length
    rainbow dispersion of sunlight into a continuous distribution of colors according to wavelength, produced by the refraction and reflection of sunlight by water droplets in the sky
    ray straight line that originates at some point
    real image image that can be projected
    refraction changing of a light ray’s direction when it passes through variations in matter
    virtual image image that cannot be projected
    zircon natural gemstone with a large index of refraction
    aberration failure of rays to converge at one focus because of limitations or defects in a lens or mirror
    accommodation the ability of the eye to adjust its focal length is known as accommodation
    adaptive optics optical technology in which computers adjust the lenses and mirrors in a device to correct for image distortions
    angular magnification a ratio related to the focal lengths of the objective and eyepiece and given as M=−fofe
    astigmatism the result of an inability of the cornea to properly focus an image onto the retina
    color constancy a part of the visual perception system that allows people to perceive color in a variety of conditions and to see some consistency in the color
    compound microscope a microscope constructed from two convex lenses, the first serving as the ocular lens(close to the eye) and the second serving as the objective lens
    eyepiece the lens or combination of lenses in an optical instrument nearest to the eye of the observer
    far point the object point imaged by the eye onto the retina in an unaccommodated eye
    farsightedness another term for hyperopia, the condition of an eye where incoming rays of light reach the retina before they converge into a focused image
    hues identity of a color as it relates specifically to the spectrum
    hyperopia the condition of an eye where incoming rays of light reach the retina before they converge into a focused image
    laser vision correction a medical procedure used to correct astigmatism and eyesight deficiencies such as myopia and hyperopia
    myopia a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than being focused on the retina
    near point the point nearest the eye at which an object is accurately focused on the retina at full accommodation
    nearsightedness another term for myopia, a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than being focused on the retina
    numerical aperture a number or measure that expresses the ability of a lens to resolve fine detail in an object being observed. Derived by mathematical formula NA=nsinα,size 12{ ital "NA"=n"sin"α}where nsize 12{n} is the refractive index of the medium between the lens and the specimen and α=θ/2size 12{α= {θ} slash {2} }
    objective lens the lens nearest to the object being examined
    presbyopia a condition in which the lens of the eye becomes progressively unable to focus on objects close to the viewer
    retinex a theory proposed to explain color and brightness perception and constancies; is a combination of the words retina and cortex, which are the two areas responsible for the processing of visual information
    retinex theory of color vision the ability to perceive color in an ambient-colored environment
    rods and cones two types of photoreceptors in the human retina; rods are responsible for vision at low light levels, while cones are active at higher light levels
    simplified theory of color vision a theory that states that there are three primary colors, which correspond to the three types of cones
    axis of a polarizing filter the direction along which the filter passes the electric field of an EM wave
    birefringent crystals that split an unpolarized beam of light into two beams
    Brewster’s angle θb=tan−1(n2/n1), where n2 is the index of refraction of the medium from which the light is reflected and n1 is the index of refraction of the medium in which the reflected light travels
    Brewster’s law tanθb=n2/n1, where n1 is the medium in which the incident and reflected light travel and n2 is the index of refraction of the medium that forms the interface that reflects the light
    coherent waves are in phase or have a definite phase relationship
    confocal microscopes microscopes that use the extended focal region to obtain three-dimensional images rather than two-dimensional images
    constructive interference for a diffraction grating occurs when the condition dsinθ=mλ (form=0,1,–1,2,–2,…) is satisfied, where d is the distance between slits in the grating, λ is the wavelength of light, and m is the order of the maximum
    constructive interference for a double slit the path length difference must be an integral multiple of the wavelength
    contrast the difference in intensity between objects and the background on which they are observed
    destructive interference for a double slit the path length difference must be a half-integral multiple of the wavelength
    destructive interference for a single slit occurs when Dsinθ=mλ,(form=1,–1,2,–2,3,…), where D is the slit width, λ is the light’s wavelength, θ is the angle relative to the original direction of the light, and m is the order of the minimum
    diffraction the bending of a wave around the edges of an opening or an obstacle
    diffraction grating a large number of evenly spaced parallel slits
    direction of polarization the direction parallel to the electric field for EM waves
    horizontally polarized the oscillations are in a horizontal plane
    Huygens’s principle every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets
    incoherent waves have random phase relationships
    interference microscopes microscopes that enhance contrast between objects and background by superimposing a reference beam of light upon the light emerging from the sample
    optically active substances that rotate the plane of polarization of light passing through them
    order the integer m used in the equations for constructive and destructive interference for a double slit
    phase-contrast microscope microscope utilizing wave interference and differences in phases to enhance contrast
    polarization the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave
    polarization microscope microscope that enhances contrast by utilizing a wave characteristic of light, useful for objects that are optically active
    polarized waves having the electric and magnetic field oscillations in a definite direction
    Rayleigh criterion two images are just resolvable when the center of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other
    reflected light that is completely polarized light reflected at the angle of reflection θb, known as Brewster’s angle
    thin film interference interference between light reflected from different surfaces of a thin film
    ultraviolet (UV) microscopes microscopes constructed with special lenses that transmit UV rays and utilize photographic or electronic techniques to record images
    unpolarized waves that are randomly polarized
    vertically polarized the oscillations are in a vertical plane
    wavelength in a medium λn=λ/n, where λ is the wavelength in vacuum, and n is the index of refraction of the medium
    classical velocity addition the method of adding velocities when v<<c; velocities add like regular numbers in one-dimensional motion: u=v+u', where v is the velocity between two observers, u is the velocity of an object relative to one observer, and u' is the velocity relative to the other observer
    first postulate of special relativity the idea that the laws of physics are the same and can be stated in their simplest form in all inertial frames of reference
    inertial frame of reference a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force
    length contraction L, the shortening of the measured length of an object moving relative to the observer’s frame: L=L01−v2c2−√=L0γ
    Michelson-Morley experiment an investigation performed in 1887 that proved that the speed of light in a vacuum is the same in all frames of reference from which it is viewed
    proper length L0, the distance between two points measured by an observer who is at rest relative to both of the points; Earth-bound observers measure proper length when measuring the distance between two points that are stationary relative to the Earth
    proper time Δt0. the time measured by an observer at rest relative to the event being observed: Δt=Δt01−v2c2√=γΔt0, where γ=11−v2c2√
    relativistic Doppler effects a change in wavelength of radiation that is moving relative to the observer; the wavelength of the radiation is longer (called a red shift) than that emitted by the source when the source moves away from the observer and shorter (called a blue shift) when the source moves toward the observer; the shifted wavelength is described by the equation λobs=λs1+uc1−uc−−−−√ where λobs is the observed wavelength, λs is the source wavelength, and u is the velocity of the source to the observer
    relativistic kinetic energy the kinetic energy of an object moving at relativistic speeds: KErel=(γ−1)mc2, where γ=11−v2c2√
    relativistic momentum p, the momentum of an object moving at relativistic velocity; p=γmu, where m is the rest mass of the object, u is its velocity relative to an observer, and the relativistic factor γ=11−u2c2√
    relativistic velocity addition the method of adding velocities of an object moving at a relativistic speed: u=v+u'1+vu'c2, where v is the relative velocity between two observers, u is the velocity of an object relative to one observer, and u' is the velocity relative to the other observer
    relativity the study of how different observers measure the same event
    rest energy the energy stored in an object at rest: E0=mc2
    rest mass the mass of an object as measured by a person at rest relative to the object
    second postulate of special relativity the idea that the speed of light c is a constant, independent of the source
    special relativity the theory that, in an inertial frame of reference, the motion of an object is relative to the frame from which it is viewed or measured
    time dilation the phenomenon of time passing slower to an observer who is moving relative to another observer
    total energy defined as E=γmc2, where γ=11−v2c2√
    twin paradox this asks why a twin traveling at a relativistic speed away and then back towards the Earth ages less than the Earth-bound twin. The premise to the paradox is faulty because the traveling twin is accelerating, and special relativity does not apply to accelerating frames of reference
    atomic spectra the electromagnetic emission from atoms and molecules
    binding energy also called the work function; the amount of energy necessary to eject an electron from a material
    blackbody an ideal radiator, which can radiate equally well at all wavelengths
    blackbody radiation the electromagnetic radiation from a blackbody
    bremsstrahlung German for braking radiation; produced when electrons are decelerated
    characteristic x rays x rays whose energy depends on the material they were produced in
    Compton effect the phenomenon whereby x rays scattered from materials have decreased energy
    correspondence principle in the classical limit (large, slow-moving objects), quantum mechanics becomes the same as classical physics
    de Broglie wavelength the wavelength possessed by a particle of matter, calculated by λ=h/p
    gamma ray also γ-ray; highest-energy photon in the EM spectrum
    Heisenberg’s uncertainty principle a fundamental limit to the precision with which pairs of quantities (momentum and position, and energy and time) can be measured
    infrared radiation photons with energies slightly less than red light
    ionizing radiation radiation that ionizes materials that absorb it
    microwaves photons with wavelengths on the order of a micron (μm)
    particle-wave duality the property of behaving like either a particle or a wave; the term for the phenomenon that all particles have wave characteristics
    photoelectric effect the phenomenon whereby some materials eject electrons when light is shined on them
    photon a quantum, or particle, of electromagnetic radiation
    photon energy the amount of energy a photon has; E=hf
    photon momentum the amount of momentum a photon has, calculated by p=hλ=E/c
    Planck’s constant h=6.626×10–34J⋅s
    probability distribution the overall spatial distribution of probabilities to find a particle at a given location
    quantized the fact that certain physical entities exist only with particular discrete values and not every conceivable value
    quantum mechanics the branch of physics that deals with small objects and with the quantization of various entities, especially energy
    ultraviolet radiation UV; ionizing photons slightly more energetic than violet light
    uncertainty in energy lack of precision or lack of knowledge of precise results in measurements of energy
    uncertainty in momentum lack of precision or lack of knowledge of precise results in measurements of momentum
    uncertainty in position lack of precision or lack of knowledge of precise results in measurements of position
    uncertainty in time lack of precision or lack of knowledge of precise results in measurements of time
    visible light the range of photon energies the human eye can detect
    x ray EM photon between γ-ray and UV in energy
    angular momentum quantum number a quantum number associated with the angular momentum of electrons
    atom basic unit of matter, which consists of a central, positively charged nucleus surrounded by negatively charged electrons
    atomic de-excitation process by which an atom transfers from an excited electronic state back to the ground state electronic configuration; often occurs by emission of a photon
    atomic excitation a state in which an atom or ion acquires the necessary energy to promote one or more of its electrons to electronic states higher in energy than their ground state
    atomic number the number of protons in the nucleus of an atom
    Bohr radius the mean radius of the orbit of an electron around the nucleus of a hydrogen atom in its ground state
    Brownian motion the continuous random movement of particles of matter suspended in a liquid or gas
    cathode-ray tube a vacuum tube containing a source of electrons and a screen to view images
    double-slit interference an experiment in which waves or particles from a single source impinge upon two slits so that the resulting interference pattern may be observed
    energies of hydrogen-like atoms Bohr formula for energies of electron states in hydrogen-like atoms: En=−Z2n2E0(n=1, 2, 3,…)
    energy-level diagram a diagram used to analyze the energy level of electrons in the orbits of an atom
    fine structure the splitting of spectral lines of the hydrogen spectrum when the spectral lines are examined at very high resolution
    fluorescence any process in which an atom or molecule, excited by a photon of a given energy, de-excites by emission of a lower-energy photon
    hologram means entire picture (from the Greek word holo, as in holistic), because the image produced is three dimensional
    holography the process of producing holograms
    hydrogen spectrum wavelengths the wavelengths of visible light from hydrogen; can be calculated by 1λ=R(1n2f−1n2i)size 12{ { {1} over {λ} } =R left ( { {1} over {n rSub { size 8{f} } rSup { size 8{2} } } } - { {1} over {n rSub { size 8{i} } rSup { size 8{2} } } } right )} {}
    hydrogen-like atom any atom with only a single electron
    intrinsic magnetic field the magnetic field generated due to the intrinsic spin of electrons
    intrinsic spin the internal or intrinsic angular momentum of electrons
    laser acronym for light amplification by stimulated emission of radiation
    magnitude of the intrinsic (internal) spin angular momentum given by S=s(s+1)−−−−−−−√h2π
    metastable a state whose lifetime is an order of magnitude longer than the most short-lived states
    orbital angular momentum an angular momentum that corresponds to the quantum analog of classical angular momentum
    orbital magnetic field the magnetic field generated due to the orbital motion of electrons
    Pauli exclusion principle a principle that states that no two electrons can have the same set of quantum numbers; that is, no two electrons can be in the same state
    phosphorescence the de-excitation of a metastable state
    planetary model of the atom the most familiar model or illustration of the structure of the atom
    population inversion the condition in which the majority of atoms in a sample are in a metastable state
    quantum numbers the values of quantized entities, such as energy and angular momentum
    Rydberg constant a physical constant related to the atomic spectra with an established value of 1.097×107m−1
    shell a probability cloud for electrons that has a single principal quantum number
    space quantization the fact that the orbital angular momentum can have only certain directions
    spin projection quantum number quantum number that can be used to calculate the intrinsic electron angular momentum along the z-axis
    spin quantum number the quantum number that parameterizes the intrinsic angular momentum (or spin angular momentum, or simply spin) of a given particle
    stimulated emission emission by atom or molecule in which an excited state is stimulated to decay, most readily caused by a photon of the same energy that is necessary to excite the state
    subshell the probability cloud for electrons that has a single angular momentum quantum number l
    x rays a form of electromagnetic radiation
    x-ray diffraction a technique that provides the detailed information about crystallographic structure of natural and manufactured materials
    z-component of spin angular momentum component of intrinsic electron spin along the z-axis
    z-component of the angular momentum component of orbital angular momentum of electron along the z-axis
    Zeeman effect the effect of external magnetic fields on spectral lines
    activity the rate of decay for radioactive nuclides
    alpha decay type of radioactive decay in which an atomic nucleus emits an alpha particle
    alpha rays one of the types of rays emitted from the nucleus of an atom
    antielectron another term for positron
    antimatter composed of antiparticles
    atomic mass the total mass of the protons, neutrons, and electrons in a single atom
    atomic number number of protons in a nucleus
    barrier penetration quantum mechanical effect whereby a particle has a nonzero probability to cross through a potential energy barrier despite not having sufficient energy to pass over the barrier; also called quantum mechanical tunneling
    becquerel SI unit for rate of decay of a radioactive material
    beta decay type of radioactive decay in which an atomic nucleus emits a beta particle
    beta rays one of the types of rays emitted from the nucleus of an atom
    binding energy the energy needed to separate nucleus into individual protons and neutrons
    binding energy per nucleon the binding energy calculated per nucleon; it reveals the details of the nuclear force—larger the BE/Asize 12{"BE"/A} {}, the more stable the nucleus
    carbon-14 dating a radioactive dating technique based on the radioactivity of carbon-14
    chart of the nuclides a table comprising stable and unstable nuclei
    curie the activity of 1g of 226Ra, equal to 3.70×1010Bqsize 12{3 "." "70" times "10" rSup { size 8{"10"} } " Bq"} {}
    daughter the nucleus obtained when parent nucleus decays and produces another nucleus following the rules and the conservation laws
    decay the process by which an atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles
    decay constant quantity that is inversely proportional to the half-life and that is used in equation for number of nuclei as a function of time
    decay equation the equation to find out how much of a radioactive material is left after a given period of time
    decay series process whereby subsequent nuclides decay until a stable nuclide is produced
    electron capture the process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino
    electron capture equation equation representing the electron capture
    electron’s antineutrino antiparticle of electron’s neutrino
    electron’s neutrino a subatomic elementary particle which has no net electric charge
    gamma decay type of radioactive decay in which an atomic nucleus emits a gamma particle
    gamma rays one of the types of rays emitted from the nucleus of an atom
    Geiger tube a very common radiation detector that usually gives an audio output
    half-life the time in which there is a 50% chance that a nucleus will decay
    ionizing radiation radiation (whether nuclear in origin or not) that produces ionization whether nuclear in origin or not
    isotopes nuclei having the same Zsize 12{Z} {} and different Nsize 12{Ns} {}s
    magic numbers a number that indicates a shell structure for the nucleus in which closed shells are more stable
    mass number number of nucleons in a nucleus
    neutrino an electrically neutral, weakly interacting elementary subatomic particle
    neutron a neutral particle that is found in a nucleus
    nuclear radiation rays that originate in the nuclei of atoms, the first examples of which were discovered by Becquerel
    nuclear reaction energy the energy created in a nuclear reaction
    nucleons the particles found inside nuclei
    nucleus a region consisting of protons and neutrons at the center of an atom
    nuclide a type of atom whose nucleus has specific numbers of protons and neutrons
    parent the original state of nucleus before decay
    photomultiplier a device that converts light into electrical signals
    positron the particle that results from positive beta decay; also known as an antielectron
    positron decay type of beta decay in which a proton is converted to a neutron, releasing a positron and a neutrino
    protons the positively charged nucleons found in a nucleus
    quantum mechanical tunneling quantum mechanical effect whereby a particle has a nonzero probability to cross through a potential energy barrier despite not having sufficient energy to pass over the barrier; also called barrier penetration
    radiation detector a device that is used to detect and track the radiation from a radioactive reaction
    radioactive a substance or object that emits nuclear radiation
    radioactive dating an application of radioactive decay in which the age of a material is determined by the amount of radioactivity of a particular type that occurs
    radioactivity the emission of rays from the nuclei of atoms
    radius of a nucleus the radius of a nucleus is r=r0A1/3
    range of radiation the distance that the radiation can travel through a material
    rate of decay the number of radioactive events per unit time
    scintillators a radiation detection method that records light produced when radiation interacts with materials
    solid-state radiation detectors semiconductors fabricated to directly convert incident radiation into electrical current
    tunneling a quantum mechanical process of potential energy barrier penetration
    Anger camera a common medical imaging device that uses a scintillator connected to a series of photomultipliers
    break-even when fusion power produced equals the heating power input
    breeder reactors reactors that are designed specifically to make plutonium
    breeding reaction process that produces 239Pu
    critical mass minimum amount necessary for self-sustained fission of a given nuclide
    criticality condition in which a chain reaction easily becomes self-sustaining
    fission fragments a daughter nuclei
    food irradiation treatment of food with ionizing radiation
    free radicals ions with unstable oxygen- or hydrogen-containing molecules
    gamma camera another name for an Anger camera
    gray (Gy) the SI unit for radiation dose which is defined to be 1 Gy=1 J/kg=100 radsize
    high dose a dose greater than 1 Sv (100 rem)
    hormesis a term used to describe generally favorable biological responses to low exposures of toxins or radiation
    ignition when a fusion reaction produces enough energy to be self-sustaining after external energy input is cut off
    inertial confinement a technique that aims multiple lasers at tiny fuel pellets evaporating and crushing them to high density
    linear hypothesis assumption that risk is directly proportional to risk from high doses
    liquid drop model a model of nucleus (only to understand some of its features) in which nucleons in a nucleus act like atoms in a drop
    low dose a dose less than 100 mSv (10 rem)
    magnetic confinement a technique in which charged particles are trapped in a small region because of difficulty in crossing magnetic field lines
    moderate dose a dose from 0.1 Sv to 1 Sv (10 to 100 rem)
    neutron-induced fission fission that is initiated after the absorption of neutron
    nuclear fission reaction in which a nucleus splits
    nuclear fusion a reaction in which two nuclei are combined, or fused, to form a larger nucleus
    positron emission tomography (PET) tomography technique that uses β+ emitters and detects the two annihilation γ rays, aiding in source localization
    proton-proton cycle the combined reactions 1H + 1H→2H + e++ve, 1H + 2H→3He + γ, and 3He + 3He→4He + 1H + 1H
    quality factor same as relative biological effectiveness
    rad the ionizing energy deposited per kilogram of tissue
    radiolytic products compounds produced due to chemical reactions of free radicals
    radiopharmaceutical compound used for medical imaging
    radiotherapy the use of ionizing radiation to treat ailments
    relative biological effectiveness (RBE) a number that expresses the relative amount of damage that a fixed amount of ionizing radiation of a given type can inflict on biological tissues
    roentgen equivalent man (rem) a dose unit more closely related to effects in biological tissue
    shielding a technique to limit radiation exposure
    sievert the SI equivalent of the rem
    single-photon-emission computed tomography (SPECT) tomography performed with γ-emitting radiopharmaceuticals
    supercriticality an exponential increase in fissions
    tagged process of attaching a radioactive substance to a chemical compound
    therapeutic ratio the ratio of abnormal cells killed to normal cells killed
    baryon number a conserved physical quantity that is zero for mesons and leptons and ±1 for baryons and antibaryons, respectively
    baryons hadrons that always decay to another baryon
    boson particle with zero or an integer value of intrinsic spin
    bottom a quark flavor
    charm a quark flavor, which is the counterpart of the strange quark
    colliding beams head-on collisions between particles moving in opposite directions
    color a quark flavor
    conservation of total baryon number a general rule based on the observation that the total number of nucleons was always conserved in nuclear reactions and decays
    conservation of total electron family number a general rule stating that the total electron family number stays the same through an interaction
    conservation of total muon family number a general rule stating that the total muon family number stays the same through an interaction
    cyclotron accelerator that uses fixed-frequency alternating electric fields and fixed magnets to accelerate particles in a circular spiral path
    down the second-lightest of all quarks
    electron family number the number ±1 that is assigned to all members of the electron family, or the number 0 that is assigned to all particles not in the electron family
    electroweak theory theory showing connections between EM and weak forces
    fermion particle with a half-integer value of intrinsic spin
    Feynman diagram a graph of time versus position that describes the exchange of virtual particles between subatomic particles
    flavors quark type
    fundamental particle particle with no substructure
    gauge boson particle that carries one of the four forces
    gluons exchange particles, analogous to the exchange of photons that gives rise to the electromagnetic force between two charged particles
    gluons eight proposed particles which carry the strong force
    grand unified theory theory that shows unification of the strong and electroweak forces
    hadrons particles that feel the strong nuclear force
    Higgs boson a massive particle that, if observed, would give validity to the theory that carrier particles are identical under certain circumstances
    leptons particles that do not feel the strong nuclear force
    linear accelerator accelerator that accelerates particles in a straight line
    meson particle whose mass is intermediate between the electron and nucleon masses
    meson hadrons that can decay to leptons and leave no hadrons
    muon family number the number ±1 that is assigned to all members of the muon family, or the number 0 that is assigned to all particles not in the muon family
    particle physics the study of and the quest for those truly fundamental particles having no substructure
    pion particle exchanged between nucleons, transmitting the force between them
    quantum chromodynamics quark theory including color
    quantum chromodynamics the governing theory of connecting quantum number color to gluons
    quantum electrodynamics the theory of electromagnetism on the particle scale
    quark an elementary particle and a fundamental constituent of matter
    standard model combination of quantum chromodynamics and electroweak theory
    strange the third lightest of all quarks
    strangeness a physical quantity assigned to various particles based on decay systematics
    superstring theory a theory of everything based on vibrating strings some 10−35m in length
    synchrotron a version of a cyclotron in which the frequency of the alternating voltage and the magnetic field strength are increased as the beam particles are accelerated
    synchrotron radiation radiation caused by a magnetic field accelerating a charged particle perpendicular to its velocity
    tau family number the number ±1 that is assigned to all members of the tau family, or the number 0 that is assigned to all particles not in the tau family
    theory of quark confinement explains how quarks can exist and yet never be isolated or directly observed
    top a quark flavor
    up the lightest of all quarks
    Van de Graaff early accelerator: simple, large-scale version of the electron gun
    virtual particles particles which cannot be directly observed but their effects can be directly observed
    stress ratio of force to area
    strain ratio of change in length to original length
    Stokes’ law Fs=6πrη, where r is the radius of the object, η is the viscosity of the fluid, and v is the object’s velocity
    static friction a forcet opposes the motion of two systems that are in contact and are not moving relative to one another
    shear deformation deformation perpendicular to the original length of an object
    magnitude of static friction fs≤μs, where μs is the coefficient of static friction and N is the magnitude of the normal force
    magnitude of kinetic friction fk=μkN, where μk is the coefficient of kinetic friction
    kinetic friction a force that opposes the motion of two systems that are in contact and moving relative to one another
    Hooke’s law proportional relationship between the force F on a material and the deformation ΔL it causes, F=kΔL
    friction a force that opposes relative motion or attempts at motion between systems in contact
    drag force

    FD, found to be proportional to the square of the speed of the object; mathematically FD∝v2 FD=1/2CρAv2,

    where C is the drag coefficient, A is the area of the object facing the fluid, and ρ is the density of the fluid

    deformation change in shape due to the application of force
    weight the force due to gravity acting on an object of mass m; defined mathematically as: w=mg, where g is the magnitude and direction of the acceleration due to gravity
    • Was this article helpful?