ELI5: how rainbows form

// eli5

What is a rainbow?

A rainbow is nature's light show that happens when sunlight shines through water droplets in the air, like after it rains. [1][5] The sun's white light gets split into all the beautiful colors we see—red, orange, yellow, green, blue, indigo, and violet.

Why does it happen?

When sunlight enters a water droplet, it slows down and bends, kind of like when you run from a hard floor onto a squishy carpet and stumble. [1][2] The light bounces inside the droplet and comes back out, and this bouncing splits the white light into all its hidden rainbow colors.

What do I need to see one?

You need two things: sunlight and water droplets in the air. [5] The best time to see a rainbow is when it's raining but the sun is still shining, or on a misty morning when the sun is behind you.

Why do rainbows always look the same?

Every time light bounces inside water droplets the same way, it always creates the same pattern of colors in the same order. [3] That's why rainbows look like curved bands of color stretching across the sky.