Halliday 2 Cap 18 - P18 061

Transcript

61. We use β = 10 log(I/Io ) with Io = 1 × 10−12 W/m2 and I = P/4πr2 (an assumption we are asked to make in the problem). We estimate r ≈ 0.3 m (distance from knuckle to ear) and find
 P ≈ 4π(0.3 m)2 1 × 10−12 W/m2 106.2 = 2 × 10−6 W .