Walker, Halliday & Resnick — Electromagnetic Waves: Problem 70

70 In Fig. 33-54a, a light ray in an underlying material is incident at angle $\theta_1$ on a boundary with water, and some of the light refracts into the water. There are two choices of underlying material. For each, the angle of refraction $\theta_2$ versus the incident angle $\theta_1$ is given in Fig. 33-54b. The horizontal axis scale is set by $\theta_{1s} = 80^\circ$. Without calculation, determine whether the index of refraction of (a) material 1 and (b) material 2 is greater or less than the index of water ($n = 1.33$). What is the index of refraction of (c) material 1 and (d) material 2?