Question

I represents intensity of sound wave, A the amplitude and r the distance from the source. Then match the following two columns.

Answer 1

$\left(A\right)$ Intensity $=\frac{P}{A}$
For a point source, $A=4\pi r^2$
$I=P/4\pi r^2$
$A\to 3$
$\left(B\right)$Since $I\propto A^2$
Therefore, $A\propto 1/r$
$B\to 2$
$\left(C\right)$Area due to a line source $=2\pi rl$
where $l$ is its length
Therefore, $I=\frac{P}{A}=\frac{P}{2\pi rl}$
$C\to 2$
$\left(D\right)$Similarly $I\propto A^2$
therefore, $A\propto 1/r^{1/2}$
$D\to 1$