Question

explain the main reason for forming of rainbow ?????

Answer 1

dispersion of light through water droplets present in the sky after rainfall is the main reason for forming the rainbow

Answer 2

the main reason for formation of rainbow is a effect which we call as dispersion of light.
it means that when a beam of white light is passed through rarer medium to denser and then again to rarer it undergoes it's splitting into different colors of light(it happens in a glass prism which must have non-parallel sides)
but in this case the beam undergoes total internal reflection too within the drop of water which splits the light into different colors which you know are VIBGYOR.

bonus information-the rainbow is not a arc it's a full circle.you just can't see what's below the horizon
bonus info-2-rainbow is curved as this happens only at a particular angle ,i.e,42° which make you the center or the Apex of like,a cone and the circular rainbow is base of that cone.

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