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Some Reflections on Light

Light originates at a given point P(a,b), reflects off a mirror tex2html_wrap_inline853 at some point R, and reaches a given point Q(c,d). It follows the path so that the total distance traveled is minimum. Prove that the angle of incidence equals the angle of reflection. Suggestion: Let tex2html_wrap_inline853 be the x-axis, and choose P and Q to lie above the x-axis.

Carl Lee
Wed Apr 21 08:26:07 EDT 1999