# The Roget Illusion and the Persistence of Vision - PowerPoint PPT Presentation

The Roget Illusion and the Persistence of Vision

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## The Roget Illusion and the Persistence of Vision

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##### Presentation Transcript

1. The Roget Illusion and the Persistence of Vision by J. L. Hunt Dept. of Physics Univ. of Guelph

2. Peter Mark Roget (1779-1869)the author of the famous Thesarusnoticed an unusual illusion

3. When a carriage wheel rolls behind A picket fence (palisade) it does NOT look like this

4. It looks like……..

5. THIS!!! Which is known as The Roget (Palisade) Illusion

6. A simple apparatus demonstrates the illusion. An endless palisade Is turned by a crank and a fixed wheel rolls behind it.

7. Here’s what you see looking at the rolling wheel through the palisade

8. Let’s follow the intersection of a spoke and a slitas the wheel rotates and the array of slits moves across.

9. This is one of the few illusions that can be analyzed mathematically. The x and y coordinates of the spoke and slit intersection are: x = rt y = x tan [2n /N + x/r] Where r = radius of the wheel  = angular velocity of the wheel N = number of spokes in the wheel n = 0……(N-1) is an index of a particular spoke.