In optical devices, optical prisms can cut a piece of glass or other transparent materials at a precise angle and plane, which can be used to analyze and reflect light. Ordinary triangular prisms can separate white light into its constituent colors, called frequency spectrum. Each color or wavelength that makes up white light can be bent or refracted, but the amount is different. Shorter wavelengths (wavelengths toward the purple end of the spectrum) bend the most, while longer wavelengths (wavelengths toward the red end of the spectrum) bend the least. This type of prism is used in some spectroscopes, instruments for analyzing light and determining the identity and structure of materials that emit or absorb light.
Optical prisms refract light to reflect (reflection prism), disperse (dispersion prism) or split (beam splitter) light. The prism is usually made of glass, but any material can be used as long as the material is transparent and suitable for the design wavelength,with common materials including glass, plastic, and fluorite.
Optical prisms can reverse the direction of light through internal reflection, so those optical prisms for sale are useful in binoculars.
Optical prisms can be made in many different forms and shapes depending on the application. For example, the Porro prism consists of two prisms. The two prisms can invert the image and are used in many optical observation instruments, such as periscopes, binoculars and monoculars.