Halliday, Resnick & Walker — Waves–II: Problem 2

In Fig. 17.1, two point sources \(S_1\) and \(S_2\), which are in phase, emit identical sound waves of wavelength \(2.0 \text{ m}\). In terms of wavelengths, what is the phase difference between the waves arriving at point \(P\) if (a) \(L_1 = 38 \text{ m}\) and \(L_2 = 34 \text{ m}\), and (b) \(L_1 = 39 \text{ m}\) and \(L_2 = 36 \text{ m}\)? (c) Assuming that the source separation is much smaller than \(L_1\) and \(L_2\), what type of interference occurs at \(P\) in situations (a) and (b)?