Why do rainbows form an arch?

Answer 1

The sun's ray should subtend a particular angle at your eye after refraction and reflection from the rain drop to see the colours.If all the raindrops which disperse colours subtend the particular angle at your eye, producing an image of all the colours observed, then the image should be in the form of the circumference of the base of a cone with your eye at the vortex of the cone.So the rainbow image is a circle and we usually see part of it ie a simi-circle.

Answer 2

A rainbow is formed when raindrops reflect (bend) sunlight toward you, breaking the light into colors. The rainbow would actually be a complete circle, but we see only part of it (an arch) because the surface of the earth is interrupting our line of vision. You can do an experiment at school with a prism to show how light can be broken into colors. (Al Peterlin)

Answer 3

Imagine how light is refracted as it enters the raindrop, then how it is reflected by the internal, curved, mirror-like surface of the raindrop, and finally how it is refracted as it emerges from the drop. If we then apply the results for a single raindrop to a whole collection of raindrops in the sky, we can visualize the shape of the arch/bow.

Answer 4

it is the way water separates the light