Prismen

Prisms, in geometry and optics, refer to two related but distinct concepts that share a common name. In geometry, a prism is a polyhedron with two parallel, congruent bases connected by rectangular or parallelogram side faces. The bases can be any polygon; the lateral faces are parallelograms, and in a right prism the lateral edges are perpendicular to the bases. The distance between the bases is called the height. The volume is the base area multiplied by the height (V = B × h). The lateral surface area equals the base perimeter times the height (L = P × h), and the total surface area is SA = 2B + L. A cross-section parallel to the bases is congruent to the base.

In optics, a prism is a transparent optical element with at least two plane surfaces that refract light. White light entering a prism is dispersed into a spectrum because refraction varies with wavelength. The amount of deviation depends on the prism angle and the material. Triangular prisms are common for dispersing light, but prisms come in many shapes, such as roof prisms, Porro prisms, and pentagonal prisms, which are used to deviate, invert, or reassemble images. Some prisms rely on total internal reflection to redirect light with high efficiency.

Applications span spectroscopy, cameras, binoculars, periscopes, and various laboratory instruments. In geometry, prisms are studied for their structural properties and symmetry, while in pedagogy they illustrate polyhedral concepts. The term prism derives from Latin and Greek roots meaning a saw or edge, reflecting the faceted nature of the shapes.