Question

The rainbow comes and disappears after sometime.How and why?

Answer 1

You need a few things to see a rainbow. The main things are rain, you need that rain to be illuminated by bright sunshine, and the rain must be in the right position relative to you. A primary rainbow is always somewhere on an arc 42 degrees around the shadow of your head (called the anti solar point). So the brightly illuminated rain must be in this direction away from you to see a rainbow. For a secondary bow it is 51 degrees around the shadow of your head.

A rainbow is caused by the refraction and internal reflection of light inside rain drops, which results in the white sunlight being separated out into the colours of the rainbow. See the detailed pages which are linked to at the top of this page for a more in depth explanation.

RAINBOW IS FORMED ONLY AFTER RAINFALL BECAUSE , AT THE TIME OF RAINFALL OR AFTER RAINFALL THERE IS A HIGH AMOUNT OF WATER IN THE ATMOSPHERE IN THE FORM OF VAPOURS OR DROPLETS . AND WHEN THE SUNLIGHT ( WHITE LIGHT ) STRIKES THE WATER VAPOURS , VAPOURS ACTING AS REFRACTING AGENT , DEFLECT THE WHITE LIGHT INTO SEVEN RAINBOW COLOURS