Rainbows are a trick of light refracting in the mist.

How to Explain to Preschoolers How a Rainbow Is Formed

by Darlene Peer

When every day begins with a "why" question and ends with another "why" question, it's inevitable that your little scientist will ask how rainbows are formed. From your child's point of view, they just magically appear after it rains. Just in case explanations of fairies and leprechauns don't work for your child, you can explain how that beautiful smudge of color in the sky formed. It all centers around the refraction of light.

Ask your child when rainbows appear. Does she know they only appear after rain? Explain that not all the water falls down to the ground and that there's still water in the air after it rains, making it feel moist.

Help your child remember a time when she's seen mist or fog. Explain that the air around where a rainbow forms has a lot of water in it, just like the fog she saw by grandma and grandpa's farm. She might not be able to see the drops as clearly because they're small, but they are there.

Explain that light refracts when it hits the water, making colors. This is the tricky part. Try putting a glass of water on a sunny window ledge or even in front of a lamp. Show her how the reflection of the light on the other side of the glass doesn't look like the lamp because it spreads out into odd shapes.

Explain that all sunlight has all the colors of the rainbow in it but you can't see those colors. Rainbows are an exception. Another way to show this, and easier to do than find a rainbow, is to use a mirror to reflect sunlight onto a wall. When you find the right angle, you'll make stripes of color.

Supervise your child while she plays with a mirror to make her own rainbows. Show her how if you tilt the mirror in a certain direction, it still reflects light but will not make a rainbow. Rainbows can only be seen under the right conditions and from the right angle.

Items you will need

  • Mirror
  • Glass of water
  • Paint or food coloring
  • Ice cube tray
  • Lamp


  • Introduce your child to the idea of blending colors to make a new color. Show how green exists between blue and yellow, then have the child blend those colors together herself to make green. This can be done with paint or by putting drops of primary color food coloring in an empty ice cube tray. Your child can use an eyedropper to combine the colors in the empty tray cups, confirming for herself that the colors of the rainbow flow naturally from one color to the next.


  • Always supervise your child while experimenting with mirrors or glasses.

About the Author

Darlene Peer has been writing, editing and proofreading for more than 10 years. Peer has written for magazines and contributed to a number of books. She has worked in various fields, from marketing to business analysis. Peer received her Bachelor of Arts in English from York University.

Photo Credits

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