Dispersion Prism

Definition

A dispersive prism is a type of optical prism, and its usual cross-sectional shape is a geometric triangle. It is the most widely known type of optical prism, although it is not commonly used in practice. Dispersion prisms are used for dispersion of light.

Principle

The property that the refractive index of a material decreases as the frequency of incident light decreases (or the wavelength increases) is called “dispersion”.
Dispersion can be achieved through instruments such as prisms or gratings that serve as “dispersion systems.”

For example, a thin beam of sunlight can be divided into seven colors of light by a prism: red, orange, yellow, green, blue, indigo, and violet. This is because the refractive index of various colors of light in complex colors are different.

When they pass through the prism, the direction of propagation is deflected to varying degrees, so when they leave the prism, they are dispersed into monochromatic light.

Bote’s Dispersion Prism

Bote’s equilateral dispersion prism is the most common dispersion element, which uses an equilateral triangle structure.

Due to the dispersion characteristics of the prism material itself, the material has different refractive indexes for light of different wavelengths. Therefore, the refraction angles and exit positions of light of different wavelengths in the prism are also different, thereby achieving the purpose of dispersion.

This type of dispersion prism produces less stray light than a diffraction grating. It eliminates common high-order problems in gratings and is a very cost-effective dispersion element.

Types of Dispersion Prism

Pellin–Broca prism

Abbe prism

Amici prism

Reflecting prism

Polarizing prism