The Complete Handbook of Optics

Chapter 1: Understanding Optics

Optics is the science and practice of controlling light. That's both simpler and more practical than it sounds. Every optical device you encounter—a camera lens, a microscope, a pair of binoculars, a laser beam used in manufacturing, a fiber-optic cable carrying internet data—is built on the same handful of physical principles. Understanding those principles and how they create tradeoffs in the real world is the foundation for choosing, using, and maintaining optical equipment correctly.

Light is electromagnetic radiation visible to the human eye, typically in the wavelength range of about 380 to 700 nanometers. But optics as a field is broader: it also deals with ultraviolet (UV) light, infrared (IR) light, and sometimes even microwave radiation, because the same fundamental rules apply. When we control light—bend it, focus it, filter it, amplify it, or transmit it—we are doing optics.

The three main mechanisms by which optics works are refraction, reflection, and diffraction.

Refraction is the bending of light as it passes from one material into another—from air into glass, for example. Light travels at different speeds in different materials. When light crosses the boundary between two materials with different optical densities, its speed and direction change, and the light bends. This bending is what allows a lens to focus light. A curved glass lens is shaped so that light rays entering it at different points are bent in a way that causes them to converge at a single focal point. That convergence is