Which of the following is not a reason behind rainbow formation?
The correct option is D. scattering.
Rainbow is formed when sunlight is dispersed by rain droplets which are suspended in air. When sunlight enters the raindrop it refracts then it undergoes dispersion and total internal reflection from the rear end of the droplet surface and again refracted out in the atmosphere and that's how we see a rainbow. So all the given process i.e total internal reflection, refraction, and dispersion take place in the rainbow formation. Scattering of light doesn't take place in the process of formation of a rainbow.