Visible Light
Light, Sound and Waves

Coloured objects in different coloured beams

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

The colour of an object depends on the illumination.

Here you can draw together ideas about apparent colours, depending on the illumination.

What to Prepare

  • A three beam projector (typically this will have three filters (red, blue and green), perhaps with mirrors to generate three separate beams from one lamp)
  • Three pieces of mounted coloured paper: Red, blue and green (choose the paper so that each only shows up in the same coloured light, but not in the other two)
  • A number of coloured everyday articles, perhaps including some provided by the pupils

What Happens During this Activity

Make sure that the three beam projector is casting three separate coloured beams, which aren't overlapping.

Take the blue paper, shown in white light, and ask for predictions as to what will be seen when it is placed in each of the coloured beams.

Try it and check the predictions. Then overlap two of the beams and again ask for predictions. Again, check the predictions.

Now overlap another pair and repeat the cycle.

Try the whole sequence again with another colour of paper. Repeat until the class is confident with the argument that a blue object looks blue because it reflects blue light, so needs to have blue light falling on it that can be reflected.

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