The science of rainbows

Welcome! I am excited to explore the science of rainbows with you. Before we dive into the physics, I would love to know a bit about your background in science or physics, and what made you interested in learning about rainbows today?

I don't have a background in physics, I'm just curious how they work!

Curiosity is the best reason to learn! You don't need any physics background at all to understand how rainbows work, as it all comes down to a few basic ideas about light and geometry.

Your path

The Physics of Light

Inside the Droplet: The Process

Variations and Rare Phenomena

At its heart, a rainbow is an created when sunlight passes through water droplets in the air, bending and bouncing the light into a arc of visible colors.

Continue to the key ingredients for a rainbow

To see a rainbow, you need three key ingredients coming together at the exact same time: sunlight, airborne water, and you.

The position of all three matters just as much as the water and light themselves. Sunlight has to come from behind you, while the rain, mist, or spray is out in front of you.

This setup aligns you directly with an imaginary spot called the —the exact point in the sky directly opposite the sun relative to your eye. Because a rainbow is an optical phenomenon formed around this point, no two people ever see the exact same rainbow. If you move, your personal rainbow moves right along with you!

Continue to the physics of light

Now we are stepping into the physics of light! To understand how light turns into a rainbow, we first have to look at what sunlight actually is.

Even though sunlight looks clear or white to us, it's actually a team effort: is a mixture of all the colors of the rainbow combined together.

Why do all the colors look white when combined?

That is a great question! It feels counterintuitive because when you mix different paint colors together, you end up with a dark, muddy brown.

The key difference is that light and paint combine in opposite ways. Paint absorbs light, but light sources add energy together. When all the colors of the —from red to violet—reach your eye at the same time, they stimulate all the color receptors in your retina equally, which your brain interprets as plain white.