Sophie Duncan on the magic of moving pictures
You need a piece of black card, a mirror and a set of 10 sequential images. These can be hand drawn on to white paper, or can be photographs with a dark background. The sequence will be repeated, and therefore the first picture in the sequence needs to follow on from the last. Bold, clear images work best - the simpler the better.
First cut out a large circle from the card - about 25cm diameter. Draw lines that divide the circle into 10 equal segments. Cut narrow slits in the card along these lines - about 5cm long and 0.5cm wide. Position each of the sequential images at the base of these slits. Pin the disk to a rubber on the end of a pencil, so that it is possible to hold the pencil and spin the disk. Stand opposite the mirror and hold up your phenakistoscope so that the images are reflected in the mirror. Hold it so that you can look through one of the slits. Now spin the card and look through the slits as they spin around. You should see your still images animated.
This toy relies on the persistence of vision. When you see something its image is retained for a fraction of a second, even when the picture has disappeared. If the first image is then replaced by a second image, the brain merges the two together and the images appear as an animated sequence. Black and white cartoon images work well, but your students may want to make their own plasticine characters and take photographs of them doing simple things such as jumping up and down.
Sophie Duncan is project manager for science at the BBC. www.bbc.co.uksn