Optics

Optics is the branch of physics that is concerned with visible 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. Geometrical optics treats light phenomena (e.g., the determination of focal points, image characteristics, etc.) through calculations derived from the geometry of rays and similar triangles.

Ancient Greek philosophers were the first to study the properties of light. They theorized that light was made up of tiny particles that could enter the eye. The idea of the particulate nature of light was widely accepted well into the late eighteenth century. A few philosophers—and later scientists from the Greek philosopher Empedocles (490–430 B.C.) to the Dutch scientist Christian Huygens (1629-1695), argued that light was actually a wave.

Following English physicist Sir Isaac Newton's (1642–1727) 1704 publication of Optics, strength for the wave interpretation of light increased. In 1800, the dual nature of light was demonstrated conclusively by the classic double slit experiment of Thomas Young. By the nineteenth century, the wave theory of light was widely accepted. In 1905 Albert Einstein's (1879–1955) photoelectric theory asserted that light behaves both as a particle and a wave.

Einstein's work extended German physicist Maxwell Planck's (1858–1947) concept of energy quantization to electromagnetic radiation.