Question

explain the formation of rainbow

Answer 1

After a rain in the fore noon or after noon when the sun rays are making  angle of 40 to 42 degrees with the horizontal then we have a possibility of  primary rainbow.

See diagram. First the Sun rays are refracted in to water drops suspended in air some hundreds of meters in to the sky.  Then those light rays are totally internally reflected and then refracted to reach the human eye at a cone angle of 40 to 42 degrees. Red color is visible on top and violet is on the bottom. The dispersion of light takes place at the last refracting surface of water drops.

A secondary rain bow is also formed with violet on top and red below other colors.
It is fainter than the primary rain bow. It is due to two total internal reflections before the light emerges out of the water drops.

Answer 2

Answer:

1) The rainbow is a spectrum of sunlight in nature.

2) The Rainbow is formed due to Dispersion of Sunlight by water droplets suspended in the atmosphere after rain.

3) This phenomenon is due to the combination of refraction of Sunlight by spherical water droplets. Which act as a prism and the total internal reflection takes place.

4) Parallel beam of Sunlight coming from sun getting dispersed at different angles of a deviation produced a cone of rays at the observers eye.

5) The rainbow, therefore appears as an arc of circle for an observer on the earth