6J11.56 - Perception - Shades of Gray
Show the shades of gray illusion that is desired. Most of these follow the same format in that a light area of gray is partially surrounded by a much darker border. The area of gray inside the border appears to be lighter than that outside. This can be more easily distinguished by putting a pencil across the lighter gray area. Removing the pencil and in some cases even covering the dark border reveals that the light gray area is uniform.
- Martin Gardner, "Two Shades of Gray?", TPT, Vol. 35, # 2, p. 119, Feb. 1997.
- Paul Doherty, Don Rathjen, "Gray Step", The Cheshire Cat, p. 61.
- Martin Gardner, "61, The Two Shades of Gray?", Smart Science Tricks, p. 94.
- Ron Hipschman, "Gray Step 4", Exploratorium Cookbook III, p. 158.1.
- Ron Hipschman, "Green Tomatoes", Exploratorium Cookbook II, p. 106.4
- Raymond Bruman, "Horse's Trail", Exploratorium Cookbook I, p. 43.1.
- Raymond Bruman, "Rotating Gray Step", Exploratorium Cookbook I, p. 44.1.
- Raymond Bruman, "Mondrian", Exploratorium Cookbook I, p. 45.1.
Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist. The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose. The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources. Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks. These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage. Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.