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 wave at P and Q is:

Correct answer: C. 9: 4 aligned & d_1=2 m_ 1 d_2=3 m Intensity 1 ( distance )^2 & I_1 (I)/(2^2) and I_2 (1)/(3^2) & (I_1)/(I_2)=(9)/(4) aligned

NEET 2005

NEET 2005 · Physics · Waves and Sound

A point source emits sound equally in all directions in a...

A point source emits sound equally in all directions in a non-absorbing medium. Two points

\mathrm{P}

and

\mathrm{Q}

are at distances of 2

\mathrm{m}

and

3 \mathrm{~m}

respectively from the source. The ratio of the intensities of the wave at

P

and

Q

is:

C. $9: 4$

\begin{aligned}& d_1=2 \mathrm{ m}_{1} d_2=3 \mathrm{ m}\\ \text{ Intensity } \propto \frac{1}{(\text{ distance })^2}\\ & I_1 \propto \frac{I}{2^2} \text{ and }I_2 \propto\frac{1}{3^2}\\ & \therefore \quad \frac{I_1}{I_2}=\frac{9}{4} \end{aligned}