Waves Ques 4
4. 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
[2005]
(a) $3: 2$
(b) $2: 3$
(c) $9: 4$
(d) $4: 9$
Show Answer
Answer:
Correct Answer: 4.(c)
Solution:
- (c) Intensity $=$ Energy/sec/unit area
Area $\propto r^{2} \Rightarrow I \propto 1 / r^{2}$
$\Rightarrow \frac{I_1}{I_2}=\frac{r_2^{2}}{r_1^{2}}=\frac{3^{2}}{2^{2}}=\frac{9}{4}$
BETA
