Question

You must have observed that a rainbow appears on the sky when sun appears immidetely after the rains

Answer 1

Yes.... I observed that a rainbow appears on the sky when sun appears.. and it is seen because of the reflection, refraction and dispersion of light in water droplets ...

Answer 2

due to the refraction light
light splits in its 7constituent colour and makes a spectrum because the tiny droplets of water per sent in air works like a tiny prism