which of the following phenomena of light are involved  in the formation of a rainbow and why  ?
1) refraction, dispersion, and total internal reflection
2) refraction, dispersion, and internal reflecton 

Three phenomenon of light which are responsible for formation of rainbow in the sky are :

1) Dispersion of sunlight by raindrops in the atmosphere.

2) Refraction of white light by different amounts due to which an arc of rainbow is formed.

3) Total internal reflection within the raindrop.

Regards