Three sources of sound S1, S2 and S3 of equal intensity are placed in a straight line with S1S2 = S2S3 (figure 16-E5). At a point P, far away from the sources, the wave coming from S2 is 120o ahead in phase of that from S1. Also, the wave coming from S3 is 120o ahead of that from S2. What would be the resultant intensity of sound at P?


Given:
All the three sources of sound, namely,
S1, S2 and S3 emit equal intensity of sound waves.
Therefore, all three sources have equal amplitudes.
A1 = A2 = A3
Now, by vector method, the resultant of the amplitudes is 0.
So, the resultant intensity at P is zero.


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