Optics is the branch of physics that is concerned with light and its properties. Physicists who focus on optics study the properties of light. They also apply these properties to phenomena such as color, mirrors, and lenses.

Ancient Greek philosophers were the first to study light. They theorized that light was made up of tiny particles that could enter the eye, creating vision. The idea of the particulate nature of light was widely accepted even past Sir Isaac Newton's (1642-1727) time, although a few people, such as the Greek philosopher Empedocles (490-430 B.C.) and the Dutch scientist Christiaan Huygens (1629-1695), believed light was actually a wave. In the nineteenth century, the wave theory of light was accepted. In 1905, Albert Einstein (1879-1955) theorized that light behaves both as a particle and a wave. This dual nature of light is the theory scientists agree upon today.

We now know...