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4.1: Reflections and phase

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    Learning Objectives

     

     

     

     

     

     

    Table \(\PageIndex{1}\)

    Links to related material

     
    Introduction to Young's experiment
    Young's experiment with water waves. The geometry: d sin θ =  for constructive interference; d sin θ = (m+½)λ for destructive interference. Phasor addition: calculating I(φ). Measuring I(φ). Interference: why does more light sometimes make the pattern darker?
    Young's experiment with single photons.
    Does the interference pattern still appear when we do it one photon at a time? Movie clips showing how individual photon capture events build up the histogram that forms the diffraction and interference patterns. Discussion of the photon puzzles.
    Molecules and photons
    Introducing the idea of quantisation: molecules as quanta of matter. Light and photons. Energy depends on wavelength. The photoelectric effect. Black body radiation
    Reflections and phases
    The phases of reflection and transmission at interfaces in one dimension: analogies with light. Animations showing phase relations for reflections air to glass and glass to air
    Thin film interference and reflections
    Reflections and phase differences. Constructive and destructive interference. Interference colours in soap bubbles. Black films. Iridescence.
    Soap bubbles
    The thinning of soap films. Surface tension and the forces involved. Minimal surfaces and geometry
    Non-reflective coatings.
    Optical pathlenght. Non-reflective coatings as examples of thin film interference: intermediate refractive index, optical pathlength difference = λ/2 for medium optical wavelengths.
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    Coherence length
    An important concent in interference: when differences in optical pathlength exceed the coherence length, phases are no longer correlated so interference is not observed.
    Newton's rings
    A thin film of air between a plano-convex lens and a glass flat. Here, thin film interference produces concentric rings of destructive and constructive interference. From the wavelength and the radii of the interference rings, we determine the radius of curvature of the lens.

    Interference Experiments
    Young's experiment, Double slit.

     


    4.1: Reflections and phase is shared under a CC BY-NC-ND 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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