A prism is a geometric solid formed by a congruent parallel and top face (also called bases) connected by edges. The sides of a prism are parallelograms.
However, for the context of optics, it's called prism the transparent optical element with straight and polished surfaces which is capable of refracting the light shining on it. The most common shape of an optical prism is a quadrangular pyramid with triangular sides.
The usual application of optical prisms is their use to separate polychromatic white light into the seven monochromatic colors of the visible spectrum, and in some situations may reflect such lights.
When white light strikes the surface of the prism, its velocity changes, however, each white light color has a different refractive index, and thus different refractive angles, reaching the other end of the prism apart.
- Dispersive Prisms They are used to separate light into their spectrum colors.
- Reflective prisms are used to reflect light.
- Polarized prisms can divide the light beam into components of varying polarity.