In this chapter, you will study optical phenomena associated with the refraction of light as it passes from one transparent material to another. The transparent material through which light travels is called the medium (plural media). Glass, water,
diamond, and quartz are all examples of transparent media through which light can pass.

Optical devices, such as cameras, microscopes, and telescopes, use the principles of reflection and refraction to create images that we can use for many scientific applications. An understanding of how lenses function is also essential to the study of optometry.