Question

What does a small droplet of water act as?

Hint:

For a rainbow to be seen, the sun must be behind the observer, and there must be water droplets (like rain or mist) in the air in front of the observer.

Answer 1

A small, spherical droplet of water acts as a tiny prism. Just like a glass prism, it refracts the incoming sunlight, disperses it into its spectrum of colors, and then reflects it internally to direct the separated colors towards the observer's eye.