Question

How rainbows are formed explain in detail in hindi if possible.

Answer 1

See, whenever we have a rainfall in the atmosphere then the water droplets remain there in the atmosphere. So when the sunlight passes through the water droplets it separates into 7 colors which we call the rainbow.
It is mainly due to the reflection, refraction and dispersion of light in the water droplets. It forms always in the opposite direction of the sun.  

Answer 2

Rainbow is caused by reflection and dispersion a daydream refraction of light waves inside droplets of water mainly when it's raining

There's a bright light source behind you that is sun with a bunch of curved mirrors in front of you that are raindrops.
The sun is putting out light in a range of wavelengths. These different wavelengths refract at slightly different angles That color display is a scientific game!
When water droplets which are still hanging out in the air after rain, are subjected to the sunlight, the light undergoes total internal reflection and emerges out from the droplet scattered in its 7 constituent colors.When the light hits the internal layer of droplet,it hits at critical angle and since the refractive index of air is less than water, it doesn't go out of drop and reflects totally. Since at a particular altitude and distance the sun rays hit the droplets such that critical angle condition is fulfilled, hence the band forms