Question

why is rainbow always formed in the direction opposite to the direction of sun?

Answer 1

Rainbows happen when sunlight and rain combine in a very specific way. The beams of sunlight separate into the colors we see in the rainbow as they enter a raindrop. Sunlight is actually made up of different colors . When a beam of sunlight comes down to Earth, the light is white. But, if the light beam happens to hit raindrops on the way down at a certain angle, the different colors that make up the beam separate so that we can see them — in the form of a rainbow.

The angle for each color of a rainbow is different, because the colors slow down at different speeds when they enter the raindrop. The light exits the raindrop in one color, depending on the angle it came in, so we see only one color coming from each raindrop. Light at different angles coming through many raindrops form the rainbow that we see, in stripes of red, orange, yellow, green, blue, indigo and violet.

Answer 2

This is because when sunlight is incident on the water droplets ,it get refracted while entering a droplet,then it is internally reflected inside on the back of the droplet and refracted again when leaving it.Due to the dispersion of light and total internal reflection, different colours reaches the observer's eyes at different angles forming the spectrum opposite to that of the sun.