Question

A surface receiving sound is moved from its original position to a position three times farther away from the source of the sound. the intensity of the received sound thus becomes

a. three times as low.
b. nine times as high.
c. nine times as low.
d. three times as high.

Answer 1

Intensity, E follows inverse square law.

E α 1/r²

r is the distance.

So if the distance r is increased by 3, the intensity would be reduced by 3²

3² = 9

So the answer is nines times as low. C.