How is a rainbow formed?
A. You need a few things to see a rainbow. The main things are rain, you need that rain to be illuminated by bright sunshine, and the rain must be in the right position relative to you. A primary rainbow is always somewhere on an arc 42 degrees around the shadow of your head (called the anti solar point). So the brightly illuminated rain must be in this direction away from you to see a rainbow. For a secondary bow it is 51 degrees around the shadow of your head. A rainbow is caused by the refraction and internal reflection of light inside rain drops, which results in the white sunlight being separated out into the colours of the rainbow. See the detailed pages which are linked to at the top of this page for a more in depth explanation. Q. Why do you see rainbows after it rains? A. You need a few things to see a rainbow. The main things are rain, you need that rain to be illuminated by bright sunshine, and you need to be in a position that the rain lies on the circle 42 degrees around t
