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Thaumatrope

In this activity, students take advantage of persistence of vision to combine two separate images.

A thaumatrope is a toy, popular in Victorian times, that uses this persistence of vision.

This illusion takes advantage of something called "persistence of vision".

When an image is shown to your eyes, the retina keeps responding for a short time (about 1/30th of a second) after the image itself has gone away. If a new picture appears just before the previous one has faded away, your brain blends the two together.

Objectives

  • Understand that visual information is processed in the brain.

Materials

Key Questions

  • What happens when you twirl the straw?

What To Do

  1. Cut out the circles containing the bird and the branch.
  2. Tape down the straw to the backside of one of the images.
  3. Tape the backs of the 2 images together, so that the straw is between them.
  4. Spin the straw between your hands. The bird should appear on the branch.

Extensions

  • Design your own thaumatrope (e.g. fish in a bowl, spider on a web etc). The only tricky part is positioning the 2 images so that they line up correctly when you twirl them.
  • How is this optical illusion similar to the Canadian Flag After-Image?