Why Are Rainbows Curved?

A rainbow is not actually shaped like a semicircle or an arc; that is simply the shape that we see. In fact, a rainbow is a circle, but we can’t see the full shape because the horizon cuts off the lower half. However, if you were flying high enough, without any disturbance, then you would be able to see a full rainbow. Rainbows appear curved because of the way sunlight reflects off of the water droplets. The light reflects off at an angle of 40-42 degrees, which creates a curved shape.