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11: Electromagnetic Waves

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    In this chapter, we explain Maxwell’s theory and show how it leads to his prediction of electromagnetic waves. We use his theory to examine what electromagnetic waves are, how they are produced, and how they transport energy and momentum. We conclude by summarizing some of the many practical applications of electromagnetic waves.

    • 11.1: Prelude to Electromagnetic Waves
      Theory predicted the general phenomenon of electromagnetic waves before anyone realized that light is a form of an electromagnetic wave. In the mid-nineteenth century, James Clerk Maxwell formulated a single theory combining all the electric and magnetic effects known at that time. Maxwell’s equations, summarizing this theory, predicted the existence of electromagnetic waves that travel at the speed of light. His theory also predicted how these waves behave and carry both energy and momentum.
    • 11.2: Maxwell’s Equations and Electromagnetic Waves
      James Clerk Maxwell (1831–1879) was one of the major contributors to physics in the nineteenth century. Although he died young, he made major contributions to the development of the kinetic theory of gases, to the understanding of color vision, and to the nature of Saturn’s rings. He is  best known for having combined existing knowledge of the laws of electricity and of magnetism with insights of his own into a complete overarching electromagnetic theory, represented by Maxwell’s equations.
    • 11.3: The Electromagnetic Spectrum
      Electromagnetic waves have a vast range of practical everyday applications that includes such diverse uses as communication by cell phone and radio broadcasting, WiFi, cooking, vision, medical imaging, and treating cancer. In this module, we discuss how electromagnetic waves are classified into categories such as radio, infrared, ultraviolet, and so on. We also summarize some of the main applications for each range.
    • 11.4: The Propagation of Light
      The index of refraction of a material is \(n = \frac{c}{v}\), where v is the speed of light in a material and c is the speed of light in a vacuum. The ray model of light describes the path of light as straight lines. The part of optics dealing with the ray aspect of light is called geometric optics. Light can travel in three ways from a source to another location: (1) directly from the source through empty space; (2) through various media; and (3) after being reflected from a mirror.
    • 11.5: The Law of Reflection
      By the end of this section, you will be able to: Explain the reflection of light from polished and rough surfaces. Describe the principle and applications of corner reflectors.
    • 11.6: Refraction
      By the end of this section, you will be able to: Describe how rays change direction upon entering a medium. Apply the law of refraction in problem solving
    • 11.7: Polarization
      Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave. The direction of polarization is defined to be the direction parallel to the electric field of the EM wave. Unpolarized light is composed of many rays having random polarization directions. Unpolarized light can be polarized by passing it through a polarizing filter or other polarizing material. The process of polarizing light decreases its intensity by a factor of
    • 11.8: Electromagnetic Waves (Exercises)
    • 11.9: The Nature of Light (Exercises)
    • 11.10: Geometric Optics and Image Formation
      This chapter introduces the major ideas of geometric optics, which describe the formation of images due to reflection and refraction.

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