"Answer This" Questions
5-A. I ntensity versus distance
Suppose you hear a firecracker go off 60 feet away from you. The intensity
you hear is 0.09 Watts/m2. What intensity would a person
who is standing 20 feet away hear?
The intensity changes as the square of the distance. Thus, if the distance is three times closer, as it is here (60/20 = 3), the intensity is 32 = 9 times as much. Since 0.09x9=0.81 W/m2, the answer is a).
© William J. Mullin