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APPARATUS

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DESCRIPTION

The four spheres form the corners of a tetrahedron.  Two faces of the tetrahedron are covered with colored paper, a light is shone through a third, and the camera views through the fourth, which will appear black if the room lights are turned off.  Reflections of reflections of reflections produce the pattern photographed above .  The pattern of triangles inside of triangles exhibits self-similarity and the boundary between the triangles is a fractal.

Shine a laser on a colored triangular region to show that the beam ends up on the corresponding piece of colored paper.  Shine the laser on a boundary and the beam can be seen through all four openings.

This may be set up in a display case.

The lamp should be shone through a translucent white filter.

Nature 399, 315 (1999) ,

TPT 37, 532 (1999) .

http://www.andamooka.org/~dsweet/Spheres/

chaotic scattering: an introduction