A rainbow is a spontaneous spectrum of sunshine that appears in the sky as bows whenever the sun falls on raindrops.
Rainbows appear due to the geometrical arrangement of raindrops. Whenever the sunbeams into the rain from behind us, incident rays of light penetrate the drop and are light refracting inwardly.
Particles are reflected from the raindrop's rear surface and refracted once again as they escape the raindrop and returned to human sight.
Rainbows are all entire circles, however, most people only see an arc or semicircle since they are on the ground and the other half is shut off by the horizon.
Rainbow is a collection of seven colors that is VIBGYOR.