These are simple toys: a card disc on a stick with a picture drawn on each side. When you twist the stick in your hands, the two pictures appear to merge into one.
Common pictures are: a bird on one side and a cage on the other, a cat on one side and a mouse on the other, a fish on one side and a bowl on the other, or two faces which appear to kiss when the stick is turned.
The ‘magic’ works because of persistence of vision. Your eye continues to see the first picture for a couple of milliseconds, so when the second picture appears, you seem to see both at the same time.
These use the same principal, but instead of two pictures merging, a strip of pictures merge together giving the illusion of smooth movement.
We made ours by cutting a cross in the centre of a paper plate, and sellotaping a marble there. This allowed the plate to spin freely and fast.
Next we used black card to make a wall around the edge with slits cut out to look through. Ideally, these slits should be equal distances apart, but the effect seems to work pretty well even if your cuts aren’t exactly equidistant.
Finally we made strips of white paper to fit inside and drew cartoons on them. I made a juggler, the children made faces that changed expression, bouncing balls, and people jumping or skipping.
Break for drink and a snack.
We talked about eyes and I showed the children a big paper picture of an eye, which they stuck post it labels on.
Then we had a go at dissecting eyes.
In small groups of three and four, the children cut open an eye and tried to identify the pupil, the iris, the cornea and the lens.
I bought the eyes from Samples for Schools. They arrive frozen.