The Reflection Property of a Parabola

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This animation demonstrates the reflection property of parabolae. (See notes below.)

A planar light wave entering a parabolic reflector is reflected by the parabola to its focus. Because every photon travels exactly the same distance (see A Proof of Quetelet & Dandelin), they all arrive at the focus simultaneously.

Of course, this animation shows only a central cross-section (that is, passing through the focus) of a mirror formed by rotating a parabola about its central axis.(11/16/07)