1. Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F-521 Email: ivan.smalyukh@colorado.edu Phone: 303-492-7277 Lectures: Tuesdays & Thursdays, 3:30 PM - 4:45 PM Office hours: Mondays & Fridays, 3:30 PM – 4:30 PM TA: Jhih-An Yang jhihan.yang@colorado.edu Class # 19

2. Midterm Exam #2 2 HW5, Due Tuesday, Nov 8 Chapter 7 – finish today Exam Overview Today/Thursday (Nov 3) Exam: Nov. 10, Thursday Science lab tour – to be announced;

3. Interesting collective behavior 3: Sensitive to a MOVING World. Time and motion important. 3 Fatigue: prolonged stimulation (staring at a lamp) causes a weaker response and a negative afterimage. Successive lightness contrast: a gray object looks darker after looking at white. Positive afterimage: We see a flash as a bright spot after it has gone away. Over stimulated nerves keep firing.

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6. Fatigue and Involuntary eye movement Eye movement moves the image around so that new areas are stimulated. Without eye movement, images fade. This has been verified by experiments that fix the image on the retina. Eye movement causes wavy lines to appear as though in motion, because the afterimage interferes with the moved image. 6

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8. The eye is moving all the time. It corrects for motion… 8 http://www.michaelbach.de/ot/mot_eyeJitter/index.html The only difference between the center and edge is the lack of any feature to “focus” on. IF there are edges, but not if edges are absent.

9. Other illusions There are many optical illusions with varying explanations. Many are poorly understood. 9

10. 10 Are the blue shades the same? Lateral inhibition cannot explain this!

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12. 12 Lateral inhibition alone does not explain this effect, the Munker-White illusion.

13. Müller-Lyer illusion 13 http://www.newworldencyclopedia.org/entry/Muller-Lyer_illusion Which arrow is longer?

14. Müller-Lyer illusion 14 http://www.michaelbach.de/ot/index.html This is the back corner of a room, it is further away, hence it must be larger.

15. Big Moon Illusion 15 What you remember.Actual

16. 16 Frankfurter illusion http://www.michaelbach.de/ot/sze_Frankfurter/index.html While focused on the background, hold your two index fingers horizontally in front of your eyes, not touching. A piece of finger will appear to float in space.

17. Are the lines straight? 17 Hering Illusion

18. Does the square have straight sides? 18

19. 19 Does the square have straight sides? 19 http://www.michaelbach.de/ot/ang_hering/index.html

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21. Poggendorff Illusion 21 http://www.michaelbach.de/ot/ang_poggendorff/index.html Are the lines continuous and straight “behind” the yellow columns?

22. Poggendorff Illusion 22 http://www.michaelbach.de/ot/ang_poggendorff/index.html

23. 23 Art that mimics 3-d.

24. Motion after effect Motion channel, keeps firing after watching a moving object, causing motion aftereffect. http://www.michaelbach.de/ot/mot_adaptSpiral/index.html The following are from Akiyoshi Kitaoka Department of Psychology, Ritsumeikan University, Kyoto, Japan: http://www.psy.ritsumei.ac.jp/~akitaoka/saishin27e.html 24

25. 25 Motion illusion (A. Kitaoka) Note that each green circle is rotated slightly from its neighbor. As your eye jumps around, it sees the circles rotation.

26. Are the ropes tangled? 26 from Akiyoshi Kitaoka

27. Motion illusion (Kitaoka) 27

28. 28 Motion illusion (Kitaoka)

29. 29 Snakes - Akiyoshi Kitaoka

30. 30 Dead Snakes - Akiyoshi Kitaoka

31. 31 Motion effects from Michael Bach’s web page Silhouette illusion Motion induced blindness Motion aftereffect (Waterfall illusion) Spiral aftereffect (motion channel activated) Breathing square http://www.michaelbach.de/ot/index.html