# 6.2: 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.

• 6.2.1: 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.
• 6.2.2: The Law of Reflection
By the end of this section, you will be able to: Explain the reflection of light from polished, rough surfaces and transparent interfaces. The section of from the interfaces of transparent media was added by J Breen.
• 6.2.3: 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
• 6.2.4: Dispersion
By the end of this section, you will be able to: Explain the cause of dispersion in a prism. Describe the effects of dispersion in producing rainbows. Summarize the advantages and disadvantages of dispersion
• 6.2.5: Superposition and Interference
Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lesser amplitude.
• 6.2.6: Diffraction
Huygens’s Principle states that every point on a wavefront is a source of wavelets, which spread forward at the same speed.
• 6.2.7: 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

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.