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Indoor Rainbows

Students experiment with white light to make their own rainbows.

To make a rainbow, white light (from the Sun) passes through and reflects back from rain droplets. Since the different colours contained in white light have different wavelengths, they are refracted through the droplets at different angles, revealing their individual colours.

Because the light you see from a rainbow has been reflected, it is polarized. You can make bits of the rainbow disappear by rotating a polarizing filter between your eye and the rainbow.

Polarizing Filter investigations and explanations can be found in this Science World Resource.

Objectives

  • Describe how different colours of light mix to give new colours.

Materials

  • Per Student or Pair:
    small glass vessel (vase, cup or bowl)
    flashlight
    mirror
    water

Key Questions

  • How is a rainbow created?
  • We can’t reproduce the Sun and rain droplets in class. What could we use to simulate both to produce our own rainbow?
  • What colours do you see in the rainbow?
  • What colour(s) was the source light?
  • What acts as the glass with the water when we see a rainbow outside?
  • When do you see rainbows across the sky? Why?

What To Do

  1. Place a mirror in the glass vessel, tilted slightly upward.
  2. Fill the glass vessel with water.
  3. Shine the white light from the flashlight through the glass at the mirror and point out the rainbow. (You may need to darken the room; rainbows should appear on the walls.)

Extensions

  • What happens if you only use the glass with no water in it? Does it still make a rainbow?
  • Try looking at the rainbow through a polarizing filter. Is the entire rainbow still there?

Other Resources

Science World YouTube | Search for Rainbows