Walker, Halliday & Resnick — Waves-II: Problem 55

55 A handclap on stage in an amphitheater sends out sound waves that scatter from terraces of width $w = 0.65 \text{ m}$ (Fig. 17-33). The sound returns to the stage as a periodic series of pulses, one from each terrace; the parade of pulses sounds like a played note. (a) Assuming that all the rays in Fig. 17-33 are horizontal, find the frequency at which the pulses return (that is, the frequency of the perceived note). (b) If the width $w$ of the terraces were smaller, would the frequency be higher or lower?