Prism

Prism, in geometry, a solid figure having 2 equal polygonal faces (the bases) lying in parallel planes and several others (the lateral faces) that are parallelograms. Prismatic pieces of transparent materials are much used in optical instruments. In spectroscopes and devices for producing monochromatic lights, prisms are used to produce dispersion effects, just as Newton first used a triangular prism to reveal that sunlight could be split up into a spectrum of colors. In binoculars and single-lens reflex cameras, inflecting prisms (employing total internal reflection) are used in preference to ordinary mirrors. The Nicol prism is used to produce polarized light.