Question

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances of 2 m and 3 m respectively from the source. The ratio of the intensities of the waves at P and Q is

• A. 3 : 2
• B. 2 : 3
• C. 9 : 4
• D. 4 : 9

Answer 1

Answer: (C)

9 : 4

Answer 2

$d_1 = 2 \,m, d_2 =3 \,m$
Intensity $?=\frac{1}{(distance)^2}$
$I_1?\frac{1}{2^2}$ and $I_2 ?\frac{1}{3^2}$
$\therefore \, \, \, \, \, \, \, \frac{I_1}{I_2}=\frac{9}{4}.$