Question

Why Rainbow is circular in shape?

Answer 1

because earth is a sphere and the firmament is circular in shape..

Answer 2

I don't think so"!!! Because If so then why the same appear when we take a water pipe and then pressing pipe water is hit to wall in sunlight or a tube-light is lighted.... again we see circular shape rainbow?????

Answer 3

perhaps it's the shape of the waves i don't know :P

Answer 4

again just let me know during electrostatic potential derivation should we take limit from infinity to that point or something else?

Answer 5

@infinity_ that is incorrect...please don't post if you're not sure of what you're talking about.

The reason is because water droplets are spherically symmetric. Oncoming light enters the water droplet, refracts inside, reflects once, and then refracts out. This process causes a cone of light to exit the water drop at an angle of about 42 degrees from the incident light (this is back towards the sun). Red light makes a slightly larger cone than blue light, so when the water droplets are at a certain angle from your line of sight, you will see only particular colors, and within the rainbow is a superposition of many colors, which is why that area is brighter. Here's a good explanation; at about 17 minutes in he begins: http://video.mit.edu/watch/how-to-make-teaching-come-alive-9843/

Answer 6

http://www.youtube.com/watch?v=uRmdZVvzMzQ
paul hewitt on the rainbow
1 min
all of his videos are really great/


in order to see the diffraction of colors from each single drop of water u need to have a specific angle between the incoming light, and the outcoming light that goes to our eye.
the drops that are in those angles are on a circle

as yakeglee said, the seperation of colors is at about 42 deg.

U can think of urself standing on the floor. now choose a spot, and poit to it to see the angle from u to the point (U can choose 42 deg). now rotate still pointing at the same angle, your finger will draw a circle! all the point on the circle are at the same angle with u.
So looking for drops with this specific angle, u'll find them all on a nice circle :)