Energy and Change Light Electricity Energy
Introduction
Questions to
think about
How we see
Reflection
Refraction
Colour
Rainbows
Changing colour
Seeing in colour
Making rainbows
Colour & energy
Scattering light
What is light?
Summary
Conclusion
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Introductory activity: Rainbows Overall management

How do you make a rainbow? Where have you seen other colours like a rainbow? Why do diamonds give the best sparkle of all the gems? Most photographs today use full colour film. Television and computer screens are almost all coloured. Even the daily newspaper has colour photographs. How do they make colour magazine photos? How are the colours created on a television screen?
A    Colours
What colours are in a rainbow and where do they come from?
What to use Hints
Triangular prism, large sheet of black cardboard with a slit taped over a brightly lit window, crystal vase sitting next to a clear 250 V lamp, slide projector with black slide with slit in middle, partly darkened room.
What to do
  1. Explore the brightly lit slit in the card on the window by looking at it through a triangular prism. Look slightly upwards (or downwards) to see the effect. What happens if you turn the prism upside down?
    Looking at a slit of light through a prism
  1. Describe what you saw through the prism when looking at the slit in the window card.
  2. List the colours in the rainbow produced by the prism.
  3. What happened when the prism was turned upside down?
  4. Shine the beam of light from the slide projector with a black slide with the slit in the middle onto a wall. What happens if your triangular prism is placed in the beam of light in front of the projector?
  5. Examine the effect the crystal vase has on the light from the clear light globe (or from sunlight).
  1. How did the triangular prism affect the light from the projector?
  2. Why did the crystal vase produce rainbows similar to that produced by the prism, but a lot more of them?
  3. Is a CD really coloured or is it silver? What range of colours can you see reflected from the surface of a CD?
    A Compact Disc
  4. Examine the bright colours on the tail feathers of a peacock. If you have a real feather, examine it to see if sections of it change colour as you move the feather around?
    A peacock feather
  1. Where else have you seen rainbow colours like this?
B    Coloured images Strategies
There are many examples of optical gadgets around us that make use of colour.
How are coloured images created?
What to use
Hand lens or powerful magnifying glass, stereo microscope (if available), access to a colour television or computer screen, a colour magazine.
What to do
  1. Examine the screen of a colour television set or computer screen using a hand lens or powerful magnifying glass.
  1. What are the three colours of the dots or stripes used to compose the television or computer screen picture?
  2. Examine the screen again. What combinations of the three colour dots seem to be used to make the following patches of colour on the screen: blue, brown, white, red, yellow, green and black?
  3. Examine a colour magazine photograph using a hand lens or powerful magnifying glass or stereo microscope.
  1. What are the colours of the dots used to compose the colour pictures in a magazine?
  2. What combinations of colour dots seem to be used to make the following patches of colour on the pictures: blue, brown, white, red, yellow, green and black?

Discussion Strategies
  1. What were the colours that your eyes could see in the rainbow?
  2. Were these colours distinct bands of colour or did these colours blend into each other? (ie was red separate from orange?)
  3. In the rainbow, was there a range of colours between the main colours you could identify? (ie was there a range of colours between blue and green?)
  4. What were the colours of the dots produced on a television screen?
  5. How does a television screen make our eyes think they are seeing all the colours of the rainbow with just three colour dots?
  6. How does a magazine photograph make our eyes think they have seen all the colours of the rainbow?

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