What causes a rainbow?

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A bright rainbow arcs over gentle waves at Karon Beach in Phuket, Thailand, with blue sky and scattered clouds above the calm sea.

$Diagram showing sunlight entering a water droplet, refracting, reflecting inside it, and emerging as separated red-to-violet light. Rays reaching an observer at about 42 degrees for red and 40 degrees for violet form a rainbow opposite the sun.$

A double rainbow arcs across a cloudy sky above a grassy meadow or field in the countryside.

What causes a rainbow?: Media

Images

A bright rainbow arcs over gentle waves at Karon Beach in Phuket, Thailand, with blue sky and scattered clouds above the calm sea.

Rainbow

Arching over the sea, a rainbow appears in Phuket, Thailand.

© Pretoperola/Dreamstime.com

$Diagram showing sunlight entering a water droplet, refracting, reflecting inside it, and emerging as separated red-to-violet light. Rays reaching an observer at about 42 degrees for red and 40 degrees for violet form a rainbow opposite the sun.$

How a rainbow is formed

As sunlight enters water droplets in the atmosphere, its constituent colors (wavelengths)...

Encyclopædia Britannica, Inc.

A double rainbow arcs across a cloudy sky above a grassy meadow or field in the countryside.

A double rainbow in stormy weather

A secondary bow above the primary bow is created by light that is reflected twice...

© sborisov/stock.adobe.com