HUESLIU'II 1U |.J. IJLJIIILII The speed of light in a medium with index of reiraction n is given by the ratio cfn. where c is the speed oi light in vacuum. Ii. dog is asked to [etch a tennis ball thrown into a lake. This dog knows calculus. i.e.. it is able to calculate the angle of incidence such that the time it takes to get there is the shortest possible. In other words. the dog takes the same path the light would take between two points. situated in two diiierent mediums. It the dog runs at a speed oi oi\" mfs and swims at a speed of 1.2 in Is. use Snell's Law to decide which pathis} will the dog take. A