When a ray of light travels from one medium to another (for example, from air to water), it changes direction. This phenomenon is known as refraction. In Figure discussed earlier, light is traveling from A to B. The amount of refraction depends on the velocities. v_1 and v_2, of light in the two media and on Fermat's Principle which states that the light's time of travel, T, from A to B, is a minimum. Find an expression for T in terms of x and the constants a, b, v_1, v_2, and c.
