Question

Rainbow is formed by splitting of sunlight in water droplets. There are millions of raindrops but we can see only one rainbow. Why is it so????

Answer 1

All of the raindrops are all spherical, all about the same size, and the sunlight it hitting them all from the same direction, so they all scatter a certain color into the same angle (they actually scatter a color in all directions, but scatter most strongly in a certain direction called the rainbow angle). If there was just one raindrop, you would see a single blip of color. Because there are many raindrops at different locations, the blips of color add together to make a bow. The reason that the colors don't all smear together into a gray blob is that certain colors are scattered mostly strongly into only certain viewing angles, because of the dispersive nature of water. Actually there is a part of the rainbow where the colors all smear together to give you a gray blob. It is the region below the colorful bow. But most people do not notice this part.