1: The Nature of Light
In this chapter, we study the basic properties of light. In the next few chapters, we investigate the behavior of light when it interacts with optical devices such as mirrors, lenses, and apertures.
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- 1.1: Prelude to The Nature of Light
- Maxwell’s equations predict the existence of electromagnetic waves and their behavior. Examples of light include radio and infrared waves, visible light, ultraviolet radiation, and X-rays. Interestingly, not all light phenomena can be explained by Maxwell’s theory. Experiments performed early in the twentieth century showed that light has corpuscular, or particle-like, properties.
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- 1.2: 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.
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- 1.7: Huygens’s Principle
- some phenomena require analysis and explanations based on the wave characteristics of light. This is particularly true when the wavelength is not negligible compared to the dimensions of an optical device, such as a slit in the case of diffraction. Huygens’s principle is an indispensable tool for this analysis. For example, according to Huygens’s principle, every point on a wave front is a source of wavelets that spread out in the forward direction at the same speed as the wave itself.
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- 1.8: 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
Thumbnail: An EM wave, such as light, is a transverse wave. The electric \(\overrightarrow{E}\) and magnetic \(\overrightarrow{B}\) fields are perpendicular to the direction of propagation. The direction of polarization of the wave is the direction of the electric field.