There is an elliptical mirror, and this mirror is defined as [tex]\frac{x^2}{a^2}+\frac{y^2}{b^2}=1[/tex]. I am supposed to use Fermat's principle to show that the light leaving a point (-c,0) is focused to a point (c,0) where [tex]c=\sqrt{a^2+b^2}[/tex](adsbygoogle = window.adsbygoogle || []).push({});

Fermat's principle state that light takes the shortest path. What I dont understand is why is the light not reflected when it hits the mirror? Shouldnt it focus back to (c,0)?

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Fermant's principle

**Physics Forums | Science Articles, Homework Help, Discussion**