Answer
(a) $P = 9.4\times 10^{-6}~W$
(b) We would need 6.4 million people to produce 60 W of normal conversation.
Work Step by Step
We can find the power output of a person speaking in normal conversation. Using Table 12-2, we can let the intensity be $3\times 10^{-6}~W/m^2$ and we can let the radius be $R = 0.50~m$.
$P = I~A$
$P = I~(4\pi~R^2)$
$P = (3\times 10^{-6}~W/m^2)(4\pi)(0.50~m)^2$
$P = 9.4\times 10^{-6}~W$
(b) We can find the number of people $N$ required to produce 60 W of normal conversation.
$N = \frac{60~W}{9.4\times 10^{-6}~W}$
$N = 6.4\times 10^6~people$
We would need 6.4 million people to produce 60 W of normal conversation.
