Prism, a transparent object surrounded by two planes that intersect but are not parallel to each other, used to split light or disperse light beams. A prism is a polyhedron made of transparent materials (such as glass, crystal, etc.). It is widely used in optical instruments. Prisms can be divided into several types according to their properties and uses. For example, the "dispersion prism" that decomposes the composite light into the spectrum in a spectroscopic instrument, the more commonly used is an equilateral prism; in a periscope, binocular telescope and other instruments, the direction of light is changed to adjust its imaging position. "Reflecting prisms" generally use right-angle prisms.