How far away should a deep sea diver be from an under-sea rock so that he can hear his own echo? (Speed of sound in water is 1500 m/s).

1500m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

750m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

150m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

75m

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Open in App

Solution

The correct option is D 75m
The sensation of sound persists in our brain for about 0.1 s.

To hear a distinct echo the minimum time interval between the original sound and the reflected sound = $0.1 s$

Speed of sound in water is given as $1500 m / s .$
Here, the sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1 s.

Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back = $1500 \times 0.1 = 150 m .$

Thus, for hearing the echo, the minimum distance of the rock from the deep sea diver must be half of this distance.
$= \frac{150}{2} = 75 m$

Answer: D

Suggest Corrections

Similar questions

Q. A sonar echo takes 8.8 s to return from a shack. How far away is the shack?

Given speed of sound in sea-water = 1533 m/s

Q. A dolphin in

25^{\circ}

C sea water emits a sound directed toward the bottom of the ocean 150 m below. How much time passes before it hears an echo?
(Take speed of sound in sea water at

25^{\circ}

C = 1530 m/s)

Q. An ultrasonic sound sent from a ship travels with the speed

1530 m s^{- 1}

in sea water. How deep is the water if the time delay of the echo from the sea bed is

6 s

(a) What is an echo? How is echo formed?

(b) What is the minimum distance in air required from a sound reflecting surface to hear an echo (at $20^{o}$ C)?

(c) A man standing 825 metres away from a cliff (steep rock) fires a gun. After how long will he hear its echo? The speed of sound in air is $330 m / s$ .

Q. The echo receiver of a sonar attached to a ship, receives the echo from the bottom of sea 4 seconds after the ultrasonic waves were sent into the sea. If the speed of the sound in water is

1500 m/s

, then what is the depth of the sea?

Join BYJU'S Learning Program