The pattern of points resulting from the successive reflections of a laser beam on two plane mirrors facing each other is contradictory to what students expect and, therefore, could motivate them to look for an explanation. A simple geometrical method is presented to solve this problem. The locus of the points is found to be a hyperbola and the locus of the light paths, a hyperboloid of revolution.

Topics
Geometrical methods, Non Euclidean geometry, Education
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© 1990 American Association of Physics Teachers.
1990
American Association of Physics Teachers
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