NTNUJAVA Virtual Physics LaboratoryEnjoy the fun of physics with simulations! Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/
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An interaction between two opposites produces a unique outcome. ..."Jules Henri Poincare(1854-1912, One of France's greatest mathematicians)"

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 Author Topic: illusion: Lilac chaser  (Read 7860 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
Fu-Kwun Hwang
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 « Embed this message on: January 03, 2011, 01:15:54 pm » posted from:Taipei,T'ai-pei,Taiwan

http://en.wikipedia.org/wiki/Lilac_chaser

Lilac chaser is a visual illusion, also known as the Pac-Man illusion. It consists of 12 lilac (or pink, rose or magenta), blurred discs arranged in a circle (like the numbers on a clock), around a small black, central cross on a grey background. One of the discs disappears briefly (for about 0.1 second), then the next (about 0.125 second later), and the next, and so on, in a clockwise direction. When one stares at the cross for about 20 seconds or so, one sees three different things:

1. A gap running around the circle of lilac discs;
2. A green disc running around the circle of lilac discs in place of the gap;
3. The green disc running around on the grey background, with the lilac discs having disappeared in sequence.

The illusion is due to three, well-known effects:

1. An illusion of movement called beta movement;
2. An afterimage in which an opposite, complementary, colourâ€”greenâ€”appears when each lilac spot disappears (if the discs were blue, one would see yellow);

The following simulation let you play with such illusion.

Embed a running copy of this simulation

Embed a running copy link(show simulation in a popuped window)
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• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.
Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

You can change the radius of the circle with slider R, select color of the dots (magnet,yellow or cyan) with it's transparance or the back-ground color(0-255 black to white).

The following is an image
Stare at the center cross for at least 30 seconds to experience the three phenomena of the illusion

 illusion_pacman.jpg (13.08 KB, 557x498 - viewed 2770 times.)  Lilac-Chaser.gif (79.19 KB, 420x420 - viewed 1344 times.) Logged
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An interaction between two opposites produces a unique outcome. ..."Jules Henri Poincare(1854-1912, One of France's greatest mathematicians)"