Notes › Fundamentals of Photonics (Saleh & Teich) Concept
Fermat’s Principle
39 words 1 min Modified
Definition (Fermat’s Principle).
Optical rays travel along the path of least time.
$$\delta \int_{A}^{B} n (\bf{r}) \ \mathrm{d}s = 0$$where $\delta$ is “the variation of” and signifies the optical pathlength is a point of inflection/minima/maxima (almost always a minima)