Explain the phenomenon of dispersion of white light through a glass prism, using suitable ray diagram.

Explanation

When the white light such as sunlight is passed through a pin to reduce it to a narrow beam. This narrow beam is made to fall on a triangular glass prism. When a white screen is held on the other side of the prism, we observe a band of seven colours on the screen.

The colour sequence obtained on the screen from its lower end is given by teh famous acronym VIBGYOR, where V stands for violet, I stands for indigo, B stands for Blue, G stands for Green, Y stands for Yellow, O stands for Orange and R stands for Red.
The red colour bends the least on passing through the prism and violet colour bends through maximum angle on passing through the prism. This is why red is at top and violet is at bottom. Thus, the phenomenon of splitting of white light into its constituent seven colours on passing through a glass prism is known as dispersion of light.