Afterimages and Optical Illusions
posted by guy on 5 May 2014 last changed 31 May 2014
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ages: 10 yrs to 99 yrs
A sequence of lessons involving effects of visual desensitization. Focuses on several optical illusions. Occupies 1 to 2 hours of class time.
|Yang and Yin - negative afterimages
|Use this lesson to give the physiological explanation behind negative afterimages. Start with the Mona Lisa or the U.S. flag illusion to get students' attention and then follow with a discussion about visual desensitization to explain how it all works. Even very young students can enjoy these illusions.
|Cheshire Cat Illusions
|Continue with this lesson to show some dramatic disappearance effects. Point out that these illusions also depend on desensitization, but they need to be fuzzy-edged to avoid being counteracted by involuntary eye movements.
|Seeing Blood Vessels in the Eye
|This effect depends on thwarting the normal desensitization in the eye. If it's possible to get a very dark room, and there are enough small flashlights to go around, this is a good activity for 10 minutes.
|Lilac Chaser Illusion
|Use this illusion as a finale. It involves both disappearance and negative afterimages. Let the students explain it. 10 minutes worth.