Why do we sometimes see double rainbows?

In one line

The rule

A double rainbow forms when sunlight is both reflected once (primary rainbow) and twice (secondary rainbow) inside raindrops, creating two separate arcs with reversed color order.

Let's understand it simply

Imagine you are playing cricket after a rain. The sun comes out, and you see a rainbow. Sometimes, you might spot a second, fainter rainbow above the first one. This is a double rainbow.

Think of each raindrop as a tiny mirror and prism. When sunlight enters a raindrop, it bends (refracts), bounces inside (reflects), and bends again as it comes out. Most of the time, light bounces once—this makes the bright main rainbow. But sometimes, light bounces twice inside the drop before coming out. This second bounce creates a second, dimmer rainbow above the first.

How it works

1. Sunlight enters a raindrop and bends (refracts) because water slows down the light.
2. Inside the drop, some light reflects off the back of the drop and comes out—this forms the primary rainbow.
3. Some light reflects twice inside the drop before coming out—this forms the secondary rainbow.
4. Each extra reflection makes the light lose energy, so the secondary rainbow is fainter.
5. The colors in the secondary rainbow are reversed because of the extra bounce.
6. Both rainbows appear as arcs, with the secondary arc outside and above the primary one.

The story behind it

The study of rainbows goes back to ancient times, but the first scientific explanation was given by René Descartes in 1637. He used glass balls filled with water to show how light bends and reflects inside drops. Later, Isaac Newton explained how white sunlight splits into many colors. The double rainbow was understood when scientists realized that light can reflect more than once inside a drop.

Where you see it in real life

• After a monsoon shower: When the sun comes out and the air is still full of raindrops, you might see a double rainbow.
• Near waterfalls: The fine mist from the water acts like tiny raindrops, creating double rainbows in the spray.
• In the fields during early morning dew: If the sun is low and there is moisture in the air, double rainbows can appear.
• From a moving bus on a rainy day: If the sun is behind you and rain is ahead, look for double rainbows.
• Garden hose spray: On a sunny day, spraying water can sometimes show both rainbows if the angle is right.
• Photographs and paintings: Double rainbows are often captured in pictures because they look magical.

Why it matters

• Shows how light works: Double rainbows help us understand how light bends and splits.
• Used in science and art: Artists and photographers use rainbows to show beauty and science.
• Weather prediction: Seeing a rainbow means the sun is shining while it is still raining—useful for farmers.
• Inspires curiosity: Double rainbows make people ask questions about nature and science.

Common mistakes

• Thinking both rainbows are equally bright: The secondary rainbow is always fainter because more light is lost with each reflection.
• Missing the reversed colors: The order of colors in the second rainbow is always opposite to the first (red is inside in the secondary, outside in the primary).
• Believing double rainbows are rare everywhere: They are common if the sunlight and raindrops are just right, but you need to look carefully.
• Forgetting the sun's position: You can only see rainbows when the sun is behind you and rain is in front.

Remember it

Double rainbow = two bounces inside the drop, two arcs in the sky, second one is fainter and colors are flipped.