Question

An object is 11 km below the sea level. A research vessel sends down a sonar signal to confirm its depth. How long will it take for the echo to reach the vessel? (Take the speed of sound in sea water as $1,520m{s}^{-1}$.

• A. 15.30 s
• B. 14.47 s
• C. 12.20 s
• D. 11.13 s

Answer 1

Answer: (B)

14.47 s

Given,

Speed of sound in sea water, $v=1520m/s$

Object's distance, $d=11km=11000m$

Time between transmission and detection, $t=?$

We know,

Distance travelled by the sonar signal

$=2\times objec{t}^{\prime }sdistance=2d=2\times 11000$

$=22000m$

Now,

$2d=speedofsound\times time$

$2d=vt$

$\Rightarrow t=\frac{2d}{v}=\frac{22000m}{1520m/s}=14.47s$

So it will take $14.47s$ for the echo to reach the vessel.