## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

(a) The sound intensity at the position of the microphone is $1.1\times 10^{-3}~W/m^2$ (b) $1.1\times 10^{-7}~J$ of sound energy impinges on the microphone each second.
(a) $I = \frac{P}{A}$ $I = \frac{P}{4\pi~R^2}$ $I = \frac{35~W}{(4\pi)~(50~m)^2}$ $I = 1.1\times 10^{-3}~W/m^2$ The sound intensity at the position of the microphone is $1.1\times 10^{-3}~W/m^2$ (b) We can find the power received by the microphone. $P = I~A$ $P = (1.1\times 10^{-3}~W/m^2)(1.0\times 10^{-4}~m^2)$ $P = 1.1\times 10^{-7}~W$ $P = 1.1\times 10^{-7}~J/s$ $1.1\times 10^{-7}~J$ of sound energy impinges on the microphone each second.