of light is
the phenomenon of splitting of white light into its constituent colors.
Dispersion happens when white light passes through a glass prism.
The different colors of light waves have different speeds in any medium
like glass. They have different bending amounts after refraction.
Hence, they show up separately beside each other.
These colors are Violet, indigo, blue, green, yellow, orange, and red.
The rainbow also is formed due to dispersion of light waves at tiny
water droplet interface with atmospheric air. Please see the diagram for
the related geometry.