What is a Rainbow? Simple Explanation for 4-Year-Old Children

Think of light as many tiny runners wearing different shoes. When they run into water (or a raindrop) they slow down, but some shoes make them slow more and some less. The colors that slow down more turn more — purple turns the most and red the least. That’s why the colors spread out and make a rainbow. Try looking at a straw in a glass of water — it looks bent because the light bent!

Great question! Sunlight looks white, but it is really lots of colors mixed together — like holding many crayons in one hand. A raindrop is a tiny round ball of water. When sunlight goes into a raindrop, the light bends (like how a pencil looks bent in a glass of water). Different colors bend by different amounts, so the colors spread out and come out of the drop in a line. Lots of drops each send out the colors in the same order, so you see a big arc of colors — a rainbow.

Want to try a little experiment with a grown-up? Put a clear glass of water on a table in bright sunlight and hold a white paper on the floor so the light shines through the glass onto the paper. Move the paper or glass until you see tiny colors appear. That shows how the drop (or glass of water) can split sunlight into many colors.