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If the distance from a point source of sound is doubled, ...

If the distance from a point source of sound is doubled, by what factor does the intensity decrease?

A.

4.00

B.

2.00

C.

0.50

D.

0.25

Correct answer is A

In general intensity of a wave is the rate of flow of energy across unit area normal to the direction of propagation of the wave intensity α1/r2 where r is the distance away from the point source. Thus if the distance from the point source of the sound wave is doubled, then the intensity will be decreased by a factor of 4