How are rainbows formed?

Explanation

(i) Rainbow is due to dispersion of sunlight through droplets of water during rainy days.
(ii) When sunlight falls on the water drop suspended in air, it splits (or dispersed) into its constituent seven colours. Thus, water drop suspended in air behaves as a glass prism.
(iii) Primary rainbow is formed when light entering the drop undergoes one total internal reflection inside the drop before coming out from the drop.
(iv) The angle of view for violet to red in primary rainbow is `40^@` to `42^@`. A secondary rainbow appears outside of a primary rainbow and develops when light entering a raindrop undergoes two internal reflections. The angle of view for red to violet in a secondary rainbow is, `52^@` to `54^@.`