A prism, a transparent object surrounded by planes that intersect but are not parallel to each other, is used to split light or disperse light beams. Prism is a polyhedron made of transparent materials (such as K9, quartz, etc.), which is an important optical element. The plane where light enters and exits is called the side, and the plane perpendicular to the side is called the main section. According to the shape of the main section, it can be divided into triangular prism, right-angle prism, pentagonal prism, pyramid prism, etc. For example, in spectroscopic instruments, the composite light is decomposed into spectral "dispersion prisms", and the more commonly used is an equilateral prism; in periscopes, binoculars and other instruments, the direction of light is changed to adjust its imaging position. "Reflecting prisms" generally use right-angle prisms.