Why Rainbow is arc shaped?

I know how rainbow is form because of water droplets in the air that act as prizim and disperse the light into seven color. But why rainbow is arc shaped?

In order to understand the fact why rainbow is actually bow-shaped, you need to have thorough knowledge of the behaviour of reflection/refraction of light rays. when the ray of light (monochrome light) enters a raindrop it is first refracted and then reflected by the internal curved surface and then finally it is refracted (bent) again when it emerges out of the drops. During this process the red ray of light emitted out by this raindrop is deviated most…and since most of the rays emitted follow the same angle of deviation, the light (color) is weaker except for this path. and this the concentration of such refracted rays at this smaller angle of deviation produces a bow-shape in rainbow.

phew! its hard to recall all that physics after such a long time

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i hope i get this right!

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From the always reliable Straight Dope:
http://www.straightdope.com/classics/a910329.html

the simple answer is because the world is curved as well.

[quote]
Originally posted by hmcq:
*the simple answer is because the world is curved as well. *
[/quote]

eh? How does earth's shape relate to the rainbow?

[quote]
Originally posted by who---me:
** eh? How does earth's shape relate to the rainbow?**
[/quote]

the horizon

Rather, because the drops of water are round and curved

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Thanks who—me, the above link is really helpful.

pumpkin, your explanation was good as I was able to dig into my memories and draw that droplet diagram show light rays refracting and reflection.

hmcq, that’s not the case as you expressed.

[This message has been edited by K-2 (edited May 02, 2002).]