Introduction to Optics
　

    For thousands of years, people have been intrigued by the behavior and properties of light. Archeologists have unearthed mirrors from ancient Egypt (c. 1900 B.C.), and there are written references to Israelite "looking-glasses" from 1200 B.C. and to Greco-Roman "burning glasses" in use 1500 years ago. While the philosophers of those eras were able to propose theories about the nature of light, the scientific study of light began in the seventeenth century with the work of Galileo, Snell, Fermat and Newton. Their theories of geometrical optics, as well as the instruments they devised, form the foundation of classical optics.

Light is a form of electromagnetic radiation that propagates as a transverse wave. In geometrical optics, the wavelength of the light is assumed to be much smaller than the physical dimensions (lengths and component sizes) of the system involved. As a result, rays, rather than wavefronts, are used to model the propagation of the light. A ray is an idealized pencil of light that travels a straight line within a homogeneous medium. Analyzing the performance of an optical system is a matter of methodically tracing representative rays.