Prove the following statement `:` A rainbow is the combined effect ( an exhibition ) of the refraction, dispersion , and total internal reflection of light ( taken together ) .
OR
With neat labelled diagram, explain how the formation of rainbow occurs.

Explanation

1. The formation of a rainbow in the sky is a combined result of refraction, dispersion, internal reflection and again refraction of sunlight by water dropletes present in the atmosphere after it has raineed.

2. The sunlight is a mixture of seven colours `:` violet , indigo, blue, green, yellow, orange and red. After it has stopped raining, the atmosphere contains a large number of water droplets. When sunlight is incident on a water droplet , there is (i) refraction and dispersion of light as it passes from air to water (ii) internal reflection of light insde the droplet and (iii) refractionn of light as it passes from water to air.
(3) The refraction index of water is different for different colours, being maximum for violet and minimum for red. Hence, there is dispersion of light ( separation into different colours) as it passes from air to water.
(4) The combined actionof different water dropletes, acting like tiny prisms, is to produce a rainbow with red colour at the outer side and violet colour at the inner side. The remaining five colours lie between these two.
The rainbow is seen when the sum is behind the observer and water droplets in the front.