Optics

Many instruments, including binoculars, cameras, magnifiers, microscopes, projectors, and telescopes, operate according to the principles of optics. All these instruments have optical devices, such as lenses and mirrors, which transmit and control light. Light is detected and measured with instruments called light meters (see Light Meter).

Scientists have used the principles of optics to increase the number of ways to use light. For example, they can transmit light along a twisted or curved path by sending the light through a filament called an optical fiber. Scientists use a device called a laser as an important and powerful light source (see Laser).

There are three major branches of optics. Physical optics deals with the nature and behavior of light as a wave. Geometrical optics is concerned with optical instruments and what happens when light strikes them. Quantum optics studies the nature of light as individual particles, known as photons.

Basic principles of optics describe what light is and how it behaves. To study visible light, scientists use a prism (wedge of glass) that produces a band of colors called the visible spectrum. Scientists analyze this and other spectra with an instrument called a spectroscope. See Light; Electromagnetic Waves; Spectrometer.

A number of different reactions may occur when light strikes the surface of an object. Diffraction, interference, reflection, and refraction are some of the basic principles that describe what may happen. Other principles include the chemical effects of light, dispersion, the photoelectric effect, and polarization. See Light.

History. The development of optics began chiefly during the 1600's. The Italian scientist Galileo built telescopes to observe the planets and the stars. Sir Isaac Newton, an English scientist, experimented with lenses and used a prism to break sunlight into its colors (see Newton, Sir Isaac). In Holland, the physicist Christiaan Huygens studied polarization and proposed a wave theory of light.

During the early 1800's, two physicists, Thomas Young of England and Augustin Fresnel of France, did much to confirm Huygens' theory. Young formulated the principle of the interference of light. Fresnel then developed a mathematical formula that supported this principle. Most scientists accepted the work of Young and Fresnel as proof of Huygens' theory.

During the mid-1800's, accurate measurements of the speed of light were made by the French scientists Armand H. L. Fizeau and Jean B. L. Foucault. At about the same time, two German scientists, Robert Bunsen and Gustav Kirchhoff, showed that atoms of chemical elements produced the color bands of the spectrum. In 1864, the British physicist James C. Maxwell introduced the electromagnetic theory of light.

Scientists made several important discoveries in optics during the late 1800's and the 1900's. Such scientists as Albert A. Michelson of the United States, Frits Zernike of the Netherlands, and Dennis Gabor of England received the Nobel Prize for physics for their work in optics.

Contributor: Brian J. Thompson, Ph.D., Provost Emeritus, Distinguished Univ. Prof., and Prof. of Optics, Univ. of Rochester.

See also Light and its list of Related Articles.

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