The splitting up of white light into seven colours on passing through a transparent medium like a glass prism is called dispersion of light.
Cause of dispersion of light:
When light passes through a prism, the different frequencies of light travel at different velocities. Because of refraction, the different velocities make the angles of refraction different, causing the light to travel in slightly different directions.
The diagram demonstrating the dispersion of white light by a glass prism is shown.
2. A glass slab acts as a combination of two identical glass prisms.