Split Light To Make A Rainbow

Split light without a prism

Want to make a rainbow but don’t have a prism? Here’s a simple way to make one anytime the sun is shining. You’ll be beaming from ear-to-ear.

Suitable for kids aged 5 +
You Need:
  • Shallow dish
  • White wall (or large piece of white paper/card)
  • Small mirror
  • Water
  • Sunlight (the stronger the better)
What to do:
  1. Pour some water into the shallow dish.
  2. Place the small mirror in the water and prop it at an angle against the side of the dish.
  3. Put the dish near a sunny window and position the mirror so that sunlight bounces off it onto a white wall.
  4. If you don’t have a white wall you can use a large piece of white card or paper attached to the wall.
  5. You should see a faint rainbow appear on the white wall or paper. If not, adjust the mirror until you see it.

Why is it so?

The water in the shallow dish acts like a prism. When the sunlight travels from air into water it slows down and bends. The seven different colours that make up white light travel at different speeds and therefore bend at slightly different angles. The mirror reflects the different colours so the rainbow spectrum appears on the wall.
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