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Over the Rainbow

Students play a modified version of the game "Octopus" to learn about the wavelength and energies of different colours of visible light.

The range of wavelengths of light that the human eye can see is called "the visible spectrum". This includes the colours of the rainbow. Each colour can be explained as a ray of light that is transmitted at a particular level of energy (with a particular wavelength):

ColourWavelength Range (nm)
Red620-750
Orange590-620
Yellow570-590
Green495-570
Blue450-495
Violet380-450

The range of wavelength for indigo is around 425–450 nm. It's hard for the human eye to distinguish and is usually considered a subset of violet.

Infrared light has a longer wavelength than red light (above 1000 nm) and can't be detected by human eyes. Some night-vision technologies involve the detection of infrared light, since objects at and around room temperature give off lots of infrared light but not much visible light.

Ultraviolet light has a shorter wavelength than violet light (below 300 nm). It can't be detected by human eyes (but can sunburn skin). A "black light" emits ultraviolet light, which can cause some paint pigments to glow.

Objectives

  • Describe how light is transmitted in waves.

Materials

  • Per Group:
    2 long ropes
    8 cones
    4 adult helpers (or designate students to be helpers, or a combination of both)
    gym or playing field

Key Questions

  • Can you name the colours of the rainbow?
  • What colour of visible light has the shortest wavelength? The longest?
  • What colour of light has the most energy? The lowest energy?

What To Do

Set up: 

  1. Set up boundaries in the shape of a large rectangular area. Designate safe zones at each end. Use the cones to mark these off.
  2. Safe Zone 1 (“start”): A pair of adult helpers stretch a long rope across the middle of the safe zone, approximately 2 metres from the boundary. This will represent a single oscillating wavelength of light for students to jump over before exiting the safe zone.
  3. Safe Zone 2 (“exit”): A pair of adult helpers stretch the long rope across the middle of the safe zone, approximately 2 metres past the boundary. This will represent a rainbow that students must jump through to reach their goal.
  4. The students assemble in the start safe zone, behind the oscillating (“wiggling”) rope.
  5. Select 2 “shadows” who will attempt to tag other students in the middle of the playing area.

Game:

  1. Remind students that different colours of light have different wavelengths. Demonstrate with one of the ropes by wiggling it back and forth.
  2. Red light has a very long wavelength, and therefore has less energy. Wiggle the rope back and forth slowly.
  3. Violet light has a very short wavelength and has more energy than red light. Wiggle the rope back and forth more quickly to illustrate.
  4. The students are designated “light beams”, and their goal is to reach the opposite safe zone without getting caught by the “shadows”.
  5. To exit the safe zone, light beams must successfully jump over the red wavelength (the rope which the adult helpers move back and forth). They then must avoid getting tagged by the shadows. Any tagged light beams become shadows themselves.
  6. Once the light beams have successfully avoided the shadows, they must enter the opposite safe zone by jumping through the rainbow (the rope being swung in a circular “skipping rope” fashion by the adults). Light beams that get caught become shadows as well.
  7. Play a few rounds with light beams running from one end of the playing area to the other.
  8. The adult volunteers can increase the speed at which the ropes are moved to correspond with different colours of light (i.e. begin round 1 with the ropes moving slowly to illustrate red light, end the game with the ropes moving quickly to illustrate the high energy and short wavelength of violet light).

Extensions

  • Is there light that has a longer wavelength than red light? What is it used for?
  • Is there light with a shorter wavelength than violet? What is it used for?

Other Resources

Science World Bonus Video |Search for Rainbows