an experiment 4 a science exhibition?

Answer 1

Here is an answer that has already been submitted to a similar question, but it is still just as good:

Try this one on for size:
Use a prism to show that white light is composed of different colors on one hand.
Then use three colored lights, red, green and blue and show that different combinations of these lights yield other colors and when all three are combined, they form white light.
As a final surprise, place a thermometer in the different colors made by the prism and record the temperatures. Then place the thermometer just outside of the red area. That is the location of Infrared so watch as the thermometer reads heat where we see no light! That shows that some forms of light are invisible.