Why are rainbows a semi-cirlce?

Question

Why are rainbows a semi-cirlce?

Answer 1

They aren't, they are circular, but the ground gets in the way, so you only see part.

More interesting is that if you are looking with two eyes, you are actually seeing two different rainbows!

Answer 2

rainbows arent actually semi-circle ist just that we see half of them if you where high up in the sky they would be a full circle

Answer 3

Proof that rainbows are a full circle:

http://www.youtube.com/watch?v=9Mo9TRHaS...

Answer 4

all to do with light refraction and angle of veiwing, and I think us mere mortals can only see part ot the light/ colour spectrum. I stand to be corrected. Given angle of veiw the veiw will be different, ie high looking down the bigger the circle, lower looking up the smaller the circle. Cool what ever angle you see one. Haven't found the pot of gold at end of yet, OK thats the non-truth part of old sayings. Good thought though.

magoo

Answer 5

Rainbows are round but the ground prevents you from seeing the full rainbow unless you are high above it...

Answer 6

thats just how we see them

Answer 7

In a band of color, all the raindrops are at the very same angle with respect to two points (your eyes and the sun) which forms a circle.  Of course there are no raindrops below the ground, which interrupts the circle.  Two people at a distance will each have a different (and personal) view of a rainbow (because of the different locations of the two points).  Raindrops are spherical and bend light separating the colors much like a prism.

Answer 8

they aren't, you only see half of it though because you are low on the ground

Answer 9

That's right, they are round and when I fly my little aircraft for example right above the clouds or fog, I sometimes see one as a circle right under me. As we pilot say: The sky is not the limit but the playground! :-)

But since, on the ground, you can't see them under you, you see them only when the sun is very low over the horison and then it looks like a semi-circle