Prism

Prism is a solid that has two parallel bases joined by three or more lateral surfaces (sides). The bases are polygons that have the same size and shape. The lateral surfaces are parallelograms.

Types of prisms include right prisms and oblique prisms. The sides of a right prism are perpendicular to its bases. The oblique prism's sides and bases are not perpendicular.
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There are many types of prisms. The simplest has triangular bases. In a right prism, the lateral surfaces are perpendicular to the bases. Prisms that do not have this property are called oblique prisms.

Prisms form an important class of optical elements. Prisms made of glass or quartz are used in a variety of instruments to change the direction of a beam of light. For example, periscopes contain right prisms that reflect light at a right angle to its original direction. In binoculars, the direction of the light is reversed after the light is reflected off two sides of the prism.

Prisms also can change the direction of a beam of light by means of refraction--that is, they can bend the light as it passes through them. The angle at which light is refracted depends on its wavelength. Different colors of light have different wavelengths. If a beam of white light, which contains all the wavelengths of visible light, passes through a prism, it is split up to form a band of colors called a spectrum. For this reason, prisms are an important part of spectrometers and other instruments that are used to measure the spectral composition of light.

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

Prism

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