Intensity of Sound: A certain factory whistle can be heard up to a distance of 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is 1.0 × 10-12 W/m2.
A. 0.079 mW
B. 0.026 mW
C. 0.26 mW
D. 0.79 mW
E. 2.6 mW
Answer: A
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