Question

The echo receiver of a sonar attached to a ship, receives the echo from the bottom of sea $4\text{s}$ after the ultrasonic waves were sent into the sea. If the speed of the sound in water is $1500\text{m/s}$, then what is the depth of the seabed?

• A. $15000\text{m}$
• B. $3000\text{m}$
• C. $3500\text{m}$
• D. $6000\text{m}$

Answer 1

The correct option is B $3000\text{m}$

As the echo took $4\text{s}$ to reach the bottom and come again to surface of echo receiver.
Let the depth of seabed from the surface be $d$
So the distance traveled by the sound wave received by the ship after reflection from the seabed $=2d$
$\because 2d=vt$
$=$ $1500\times 4=6000$
$⟹d=3000\text{m}$
So the depth of the seabed is $3000\text{m}$ or $3\text{km}$.