A source of sound waves is placed at the center of a very large sound-reflecting wall. The source emits 0.500 W of power. Two meters from the source the intensity in W/m² is A) 9.95 × 10−³. B) 1.99 × 10−². C) 0.313. D) 0.399. E) 0.625.

Question

Quizplus · Accepted Answer

The formula relating intensity and power is:

$I=\frac{P}{4\pi r^2}$

where $r$ is the distance from the source. Plugging in the given values:

$I=\frac{0.500	ext{ W}}{4\pi (2	ext{ m})^2}=1.99	imes10^{-12}	ext{ W/m}^2$

This is choice (B).

A Source of Sound Waves Is Placed at the Center