(a) If the amplitude of the wave generated by each source in Figure 17.16 is \(A\) at points \(\mathrm{P}\) and \(\mathrm{Q}\), what is the overall amplitude at \(\mathrm{P}\) in Figure 17.16 a? In Figure 17.16 b?

(b) Given that the wave energy that passes \(Q\) in Figure \(17.16 b\) becomes zero when \(S_{1}\) is turned on, do you expect the energy that passes \(P\) to increase or decrease?

(c) Use your answer to part \(a\) to determine by what factor the amount of energy that passes \(P\) changes, and reconcile your answer with your answer to part \(b\).

Transcribed Image Text:

Figure 17.16 Less can be more. (a) When both sources generate waves, point Q lies on a nodal line and thus never experiences displacement of the medium (because the waves from the two sources interfere destructively there). If these were sound waves, there would be silence at Q. (b) However, when only one source generates waves, Q experiences their full effect. (a) Both sources generate waves (b) Only S, generates waves