What is a prism?


Prisms made of glass or quartz glass are used in optics to change the optical path, to redirect light through total reflection at a certain angle, or to split it into its individual wavelengths using glass for dispersion of the light. While right-angled prisms are mostly used for redirecting and extending the path, equilateral prisms with three 60° angles are often used to split the light. These are therefore also called dispersion prisms. To split light into its individual wavelengths, diffraction gratings are used more often than prisms. They produce higher dispersion that, unlike prisms, is not dependent on wavelength.


right-angled prism for 90° deflection (left), dispersion prima for spectral splitting (right)

How does a prism work?

For the redirection of light, the light is usually totally reflected at a glass/air transition. A dispersion prism uses dispersion caused by glass to split light into its individual wavelengths.


What is an optical prism made of?

An optical prism usually consists of glass or quartz glass.

Why do we need a prism?

A prism is required if the optical path needs to be changed, the light needs to be redirected by total reflection at a certain angle, or if light must be split into its individual wavelengths.