Chapter 17, Problem 19P

GO Figure 17-35 shows two isotropic point sources of sound, S₁ and S₂. The sources emit waves in phase at wavelength 0.50 m; they are separated by D = 1.75 m. If we move a sound detector along a large circle centered at the midpoint between the sources, at how many points do waves arrive at the detector (a) exactly in phase and (b) exactly out of phase?

Figure 17-35 Problems 19 and 105.