Snell’s law describes how light rays bend when they pass from air into water, as they do when the sun shines into a swimming pool. Light moves more slowly in water, much like the hiker in the snow, and it bends accordingly to minimise its travel time. Similarly, light bends when it travels from air into glass or plastic, as when it refracts through your eyeglass lenses. The eerie point is that light behaves as if it were considering all possible paths and then taking the best one. Nature — cue the theme from The Twilight Zone — somehow knows calculus.
One of many anecdotes I picked up from Steven Strogatz's recent book 'The Joy of X: A Guided Tour of Mathematics, from One to Infinity'. It is a "pop-maths" book designed to re-introduce the subject to people who have long forgotten it! Well worth the read!
Copyright © Chola Mukanga 2013