Ptolemy, who lived in the city of Alexandria in Egypt during the second century AD, gave the measured values in the following table for the angle of incidence θ1 and the angle of refraction θ2 for a light beam passing from air into water. Do these values agree with Snell’s Law? If so, what index of refraction results? (These data are of interest as the oldest recorded physical measurements.)
Light sound, and other waves travel at different speeds, depending on the media (air, water, wood, and so on) through which they pass. Suppose that light travels from a point A in one medium, where its speed is v1, to a point B in another medium, where its speed is v2. Refer to the figure, where the angle θ1 is called the angle of incidence and the angle θ2 is the angle of refraction. Snell’s Law, which can be proved using calculus, states that
The vl/v2 is called the index of refraction. Some values are given in the table shown to the right.
