Diagram of a triangular prism, dispersing light

Lamps as seen through a prism.

In optics, a triangular prism is a type of optical prism with the shape of a geometrical triangular prism. It is the most widely-known type of optical prism, although perhaps not the most common in actual use. Triangular prisms are used to disperse light, that is to break light up into its spectral components. This dispersion occurs because the angle of refraction is dependent on the refractive index, which in turn is dependent on the wavelength. This effect can also be used to measure the refractive index of the prism's material with high accuracy. Table of Opticks, 1728 Cyclopaedia Optics ( appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ... If a shaft of light entering a prism is sufficiently small such that the coloured edges meet, a spectrum results In optics, a prism is a device used to refract light, reflect it or break it up (to disperse it) into its constituent spectral colours (colours of the rainbow). ... In geometry, a triangular prism or three-sided prism is a polyhedron made of a triangular base, a translated copy, and 3 faces joining corresponding sides. ... Dispersion of a light beam in a prism. ... In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The wavelength is the distance between repeating units of a wave pattern. ...

Although the refractive index is dependent on the wavelength in every material, some materials have a much stronger wavelength dependence (are much more dispersive) than others. Normal optical BK7 glass has a relatively small dispersion, while glass types such as LaSF11 have a much stronger dispersion and hence are more suitable for use in dispersive prisms.

The top angle of the prism (the upper corner in the accompanying picture) can be chosen to influence the exact dispersion characteristics. However, it is typically chosen such that both the incoming and outgoing light rays hit the surface approximately at the Brewster angle, so that reflection losses are minimized. An illustration of the polaristion of light which is incident on an interface at Brewsters angle. ... Spheres reflecting the floor and each other. ...