Halliday, Resnick & Walker — Interference: Problem 71

71 Suppose that the two waves in Fig. 35-4 have wavelength \(\lambda = 610 \text{ nm}\) in air. What multiple of \(\lambda\) gives their phase difference when they emerge if (a) \(n_1 = 1.50\), \(n_2 = 1.60\), and \(L = 7.00 \mu\text{m}\); (b) \(n_1 = 1.62\), \(n_2 = 1.72\), and \(L = 7.00 \mu\text{m}\); and (c) \(n_1 = 1.83\), \(n_2 = 1.59\), and \(L = 2.16 \mu\text{m}\)? (d) Suppose that in each of these three situations the waves arrive at a common point (with the same amplitude) after emerging. Rank the situations according to the brightness the waves produce at the common point.