Question

what is meant by dispersion of light?

Answer 1

The phenomenon of splitting of white light by a prism into its constituent colours is known as dispersion

Answer 2

Dispersion 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.