What Shape is a Rainbow?

A rainbow is a circular arc or bow-shaped spectrum of light.

How Is a Rainbow Formed?

Rainbows form when sunlight passes through raindrops in the atmosphere. The light bends (refracts), reflects inside the raindrop, and then bends again as it exits, splitting into colors.

• Circular arc: Because light bends at a specific angle (about 42 degrees), a rainbow appears as a curved arc in the sky.
• Full circle: From an airplane or high viewpoint, rainbows can be seen as full circles, but from the ground, the horizon blocks the bottom half.

Why Does It Appear as an Arc?

The ground prevents us from seeing the full circle, so only the top part of the circle is visible, forming the familiar bow shape.

Colors of the Rainbow

A rainbow displays seven main colors: Red, Orange, Yellow, Green, Blue, Indigo, and Violet (ROYGBIV), arranged from the outer edge to the inner edge.