…until 1600 and something, or 15, 16, I guess, 1621, that finally someone found the rule connecting these two angles. That was Mr. Snell, and his rule is the following. If this is called the angle in, then this is called the angle out. Then it turns…

…were doing something when we look at it. Now I'd like to demonstrate that the principle of least time will give the law of Snell. Well, you must, however, make an assumption about the speed of light in water. I'm going to assume that the speed in light…