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I was cooking and noticed a funny pattern appearing when i was looking in on of my pans. When light fell into a pan with high edges, it seemed to reflect into a hart-shaped pattern. Can anyone explain how the light gets warped into this shape, and does anyone know why the light gets reflected into a sharp line, rather then a hart-shaped plane?

I have added some pictures to make it more clear.

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You want to look up Caustics in optics.

The specifics of your example boil down to the way the geometry works out. In this case the simplest model would be something like a Nephroid, where you have a circular shape which ( in terms of illumination ) is similar to a half circle, and that makes that particular caustic.

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  • $\begingroup$ Thanks! This is indeed the shape: en.m.wikipedia.org/wiki/Nephroid#/media/…. However, it is still unclear to me how the light rays get reflected this way. Is there a way to compose some sort of ray diagram? $\endgroup$ – Sebas Smits Jan 7 '17 at 14:23
  • $\begingroup$ The curve is tangential to all the light rays reflected from the surface. To get this curve you need to trace all the reflections, but tracing several of them will generally give you an idea of the curve. Of course this is an idealized case and real world surfaces don't produce such perfect results. The computer graphics people may actually know more about these than anyone else as it's a concept used in many 3D graphics applications. $\endgroup$ – StephenG Jan 7 '17 at 18:32
  • $\begingroup$ "...boil down..." - I get it :) $\endgroup$ – uhoh Apr 8 '17 at 12:51

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