Why rainbow is in shape of circle?

Question

Why it can't be in square or even triangle shape? Is this related to refraction?

Answer 1

It is a bit hard to explain 3-d optics since it is basically up to you to visiualize the rays instead of seing them drawn. But at least I can try:

You might have realised the rainbow is always in a specific orientation with respect to the sun. This, as well as the circular shape has to do with the refraction effect caused by the water vapor in the air (usually after a rain or mist).

The light coming from the sun is refracted at different angles for different colors (providing the colorful nature of the rainbow), but the main point is that the angles are defined from the normal line between your eyes and the sun. Therefore, the rainbow will be seen as a circle around this normal line - of course, if the sun is not at the top or you are not on a plane*, you cannot see a total circle rainbow, since some of it would be blocked by the earth.

* By the way, even if you are on a plane it is highly unlikely to see a rainbow, since water vapor tends to stay low in the atmosphere.

Answer 2

It is related to the position of the observer and the raindrop and the light source..

Now ask why you don't normally see a rainbow at noon....

Answer 3

It's and arc, representing God's bow as a convent between us not to destroy all mankind again by water, so the bible say's..Yes it's light being refracted thru the mist. And since the earth is round and we can only see from horizon to horizon, we see the arc.

Answer 4

bcoz the earth is round,..the atmosphere surrounding it is also roughly round,hence the rainbow effect of the atmosphere which we see is also round,ok?

Answer 5

this is because how light bends. such as red light bends less than violet light.