Name the two phenomena involved in the formation of a rainbow.

(N/A) The formation of a rainbow is primarily caused by the following two phenomena:
$(i)$ Dispersion: When sunlight enters a water droplet,it splits into its constituent colors due to the difference in refractive indices for different wavelengths.
$(ii)$ Total Internal Reflection: After dispersion,the light rays strike the inner surface of the water droplet and are reflected back inside,which is known as total internal reflection.