Chapter 25, Problem 16PE

Figure 25.54 shows a ray of light passing from one medium into a second and then a third. Show that θ₃ is the same as it would be if the second medium were not present (provided total internal reflection does not occur).

Figure 25.54 A ray of light passes from one medium to a third by traveling through a second. The final direction is the same as if the second medium were not present, but the ray is displaced by $△x$ (Shawn exaggerated).