Two people are talking at a distance of 2.0 m from where you are and you measure the sound intensity as 1.5 * 10^-7 W/m².Another student is 8.0 m away from the talkers.What sound intensity does the other student measure?

Question

Quizplus · Accepted Answer

The sound intensity decreases with the square of the distance, so the other student will measure a lower sound intensity. Using the inverse square law:

I1/I2 = (r2/r1)^2

where I1 is the original sound intensity (1.5 x 10^-7 W/m^2), r1 is the original distance (2.0 m), r2 is the new distance (8.0 m) and I2 is the new sound intensity.

I2 = I1 x (r1/r2)^2 
I2 = 1.5 x 10^-7 x (2.0/8.0)^2 
I2 = 9.4 x 10^-10 W/m^2

Therefore, the other student measures a sound intensity of 9.4 x 10^-10 W/m^2, which is option A.

Two People Are Talking at a Distance of 2