Child Science Experiments: Rainbow Pinwheel
This is one of the simplest and fun of all young child science experiments. Cutting, pasting, gluing and bright colours all come together in this investigation of the nature of white light. The rainbow pinwheel will do the exact opposite of the rainbow: it will turn rainbow colours into white light. Materials Needed: ** cardboard circle of about 30cm (12in) diameter. This can be from any old box. It would help to use a compass to get the circle just right. Procedure: You will need to cut out 7 wedges of colour so they arrange around the centre of the circle, as shown in the picture to the right. The wedges need to be each the same size. If you are using a protractor, the angle of each wedge is 51.4 degrees. Paste these wedges onto the cardboard circle in the order shown. Put the pin through the centre of the cardboard circle and pin it to the flat end of the piece of dowel. It must be loose enough to spin freely. Take the pinwheel outside into bright light. Spin it as fast as you can and see what happens. What Is Happening? White light is made of these seven colours blended together. By spinning the wheel fast, the colours blur together and so the wheel appears white. The faster you spin it, the whiter it looks. Possible Extension Activities Complementary Colours: For older children, this same project can be used to demonstrate the complements of the colours of the rainbow. This requires wedges of colour that have a 60 degree angle so that six of them fit neatly onto the pinwheel.
The idea is to remove the colour to be tested, then spin the wheel and see what the resulting colour is. This colour is often referred to as the opposite colour of the one that has been removed. The term complement, meaning making up the rest, is far more accurate.The notion of complementary colours is not easy to understand without experiencing it in a form such as this experiment. It comes into use in senior secondary school Chemistry as a method of concentration analysis for solutions. Doing child science experiments like this one with your child is building a firm base of knowledge to promote later success in schooling.
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