Question

For hearing an echo the minimum distance between the source of sound and the reflecting body should be

• A. $12m$
• B. $24m$
• C. $17m$
• D. $51m$

Answer 1

The correct option is C

$17m$

1. Any sound persists in the human ear for $\frac{1}{10}second$.
2. If the velocity of the sound is $332$ ms^-1.
3. The minimum distance is calculated by,
4. $d=\frac{v\times t}{2}$
5. $v-$The velocity of sound in water.
6. $t-$ Time taken by the echo to travel back to the trawler.
7. $d=\frac{332\times 0.1}{2}$
8. $d=\frac{33.2}{2}$
9. $d=16.6m\left(approx\right)$

Hence, $17m$ is the minimum distance required between the sound source and the reflecting body.