prism

A prism is a solid in three-dimensional geometry with two parallel, congruent bases connected by faces that are parallelograms. The bases are polygons, and the side faces join corresponding vertices of the bases. If the joining edges are perpendicular to the bases, the prism is right; otherwise it is oblique. A prism with an n-gon base is called an n-prism. The volume equals the base area B times the perpendicular height h (V = B h). The surface area is 2B plus the lateral area, which equals the base perimeter P multiplied by h.

In optics, a prism is a transparent object with flat surfaces that refract light. Light entering a prism changes speed and direction, often dispersing into a spectrum of colors. Common prisms are made of glass or quartz; their exact effect depends on geometry and the material. Triangular prisms are widely used to deviate light and to disperse colors, while other shapes such as roof prisms and Porro prisms are used to alter image orientation in instruments like binoculars and cameras. Prisms underpin a range of devices, including spectrometers and laser setups; their behavior is described by Snell's law and, where appropriate, total internal reflection.

In mathematics, prisms are a basic class of polyhedra studied for their symmetry and tiling properties, as well as for practical applications in design. The term is also used metaphorically in science and culture to describe a medium through which something is perceived, interpreted, or filtered.