Question

On sending an ultrasonic wave form a ship towards the bottom of a sea, the time interval between sending the wave and receiving it back is found to be 1.5 s. If the velocity of wave in sea water is 1400 $m{s}^{-1}$ find the depth of the sea.

• A. 1050 m
• B. 950 m
• C. 1000 m
• D. 1150 m

Answer 1

Answer: (A)

As the speed of sound in seawater is 1400 m/s in the question, the distance travelled by sound(ultrasonic wave from the ship) in 1.5 seconds is calculated from the formula
$Distancetraveled=velocityofsound\times timetaken$.

That is, $Distance=1400m/s\times 1.5s$ $=2100m.$

This is twice the minimum distance between a source of sound (ship) and the reflector (sea bed) as it is reflected sound.

So, the sea bed is at a distance of 1050 m at least from the ship. Therefore, the depth of the sea is 1.05 km.