Question

explain how the formation of rainbow occurs?

Answer 1

Rainbow occurs due to the phenomenon of dispersion of white light from Sun when it comes out of water droplets suspended in air hundreds of meters above Earth's surface.

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Details:

       After a rain in the fore noon or after noon when the sun rays are making an angle of 40 to 42 degrees with the horizontal then we have a possibility of  primary rainbow. There are millions of rain drops suspended in air after a rain above earth’s surface.

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.  The refraction of white light at the exit from rain drop results in a dispersion.

          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. This is visible to us as the VIBGYOR color bands in a semicircular arc in the sky. Actually the rainbow is a full circle within the cones angles of 40 to 42 degrees.

           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 with refraction. The refraction gives rise to dispersion of white light.

 

Answer 2

Rainbow consist of seven color ...and when White Light gets dispersed or Dispersion of White Light takes place ....so...it 7 wonderful colors comes out of it..
They are
1.Violet
2.Indigo
3.Blue
4.Green
5.Yellow
6.Orange
7.Red

Red gets dispersed the least and Violet dispersed the most....