Question

name the phenomenon involved in the formtion of rainbow

Answer 1

Dispersion of light.
Drops of water acts like a glass prism and sunlight acts like a source of white light.
hope it helps.

Answer 2

During the formation of rainbow, three phenomenon are involved. They are :

Refraction of sunlight 
Total internal reflection of sunlight inside the raindrop 
Dispersion of sunlight into 7 colours.

These are the phenemenon involved in the formation of rainbow.

Hope it helps!!
Cheers!!