College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 74

Figure P22.26 shows a light ray incident on a series of slabs having different refractive indices, where n 1 n 2 n 3 n 4. Notice that the path of the ray steadily bends toward the normal. If the variation in n were continuous, the path would form a smooth curve. Use this idea and a ray diagram to explain why you can see the Sun at sunset after it has fallen below the horizon.