Fermat's Principle: Finding the Minimum Time for Light to Travel

Physics Ninja looks at Fermat's Principle using 3 different methods. In part 1 a simple numerical example is presented. In part 2 (time: 14:42) we use a calculus approach to find the minimum time and show that it corresponds to Snell's Law. In part 3 (time: 19:46) I show how to solve this problem using the Euler-Lagrange Equation.