A source of sound waves is placed at the centre of a very large sound-reflecting wall. The source emits 0.500 W of power. Two metres 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

We can use the formula for sound intensity in terms of power and distance: $I = \frac{P}{4\pi r^2}$ where $P$ is the power in watts and $r$ is the distance from the source in meters. Plugging in the given values, we get: $I = \frac{0.500}{4\pi (2)^2} = 0.0199$ W/m$^2$ Converting to scientific notation, we have: $I = 1.99 imes 10^{-2}$ W/m$^2$ Since the question asks for the intensity in W/m², we need to express the answer in scientific notation with three significant figures, which gives us: $I = 1.99 imes 10^{-2}$ W/m$^2 \approx 1.99 imes 10^{-2}$ W/m² Therefore, the best choice is B.

A Source of Sound Waves Is Placed at the Centre