How do rainbows form and why do they always appear as arcs?

Rainbows are like colorful arks made by sunlight and water droplets working together.

When it rains and the sun comes out, water droplets in the air act like tiny mirrors. Each droplet splits the white light from the sun into all its colors, red, orange, yellow, green, blue, indigo, and violet, just like how a prism works. This is called refraction.

Imagine you're playing with a glass of water on a sunny day. When the light goes through the glass, it changes direction, that’s bending, or refraction. The same thing happens in raindrops. Each color bends just a little differently, so they spread out into a line of colors.

Now imagine you're holding a round balloon and shining a flashlight at it from one side. You’d see a circle of light on the wall, but if you’re only looking at part of that circle, like a slice of pizza, it looks like an arc. That’s what happens with rainbows!

You see an arc because you're only seeing part of the full circle of colors, the rest is hidden behind you or the ground. So next time you see a rainbow, imagine it as a giant colorful pizza slice in the sky!