The Inverse Square Law – Practice


1) The sound emitted from a speaker has an intensity of 8 × 103  Wm2. Calculate the intensity of the sound 10m from the speakers:

2) The intensity of a sound wave is 6 × 10Wm2 at a distance of 4m from the source. What is the intensity of the sound at a distance of 10m from the source?

3) An observer at 40m measures the intensity of a sound to be 1.0 × 10Wm2. What would an observer at 10m measure the intensity to be?

4) How far away from a source would an observer need to be if the intensity of the sound they hear is 10% of the original sound?

Quick Answers:

1) 8 × 10−5 Wm−2 

2) 9.6 × 10−4 Wm−2 

3) 1.6 × 10−4 Wm−2 

4) 3.16m

Worked Answers: