Question

Q. An ultrasound was detected after 4 seconds when sent from sea to bottom of ocean. If the speed of sound in water is 1500 m/s, find the depth of the sea.
1. 1.5 km
2. 2 km
3. 2.5 km
4. 3 km

Answer 1

Correct Answer - Option 4 : 3 km

Concept:

Ultrasound

• The sound whose frequency is more than 20,000 Hz is known as ultrasound. 
• This has many applications in science and technology. 
• This due to its ability to travel along well-defined paths even in the presence of obstacles.
• SONAR (Sound Navigation And Ranging) uses ultrasonic waves to measure the distances and other related parameters of any object. 

Calculation:

Speed of sound s = 1500 m/s

time t = 4s

depth d = ? (we have to calculate)

Now, in order to reach the ground and come back, the sound has to travel 2d distance.

distance = speed × time

2d = 1500 m/s × 4s = 6000 m

⇒ 2d = 6000 m

⇒ d = 3000 m = 3 km

So, the dept is 3 km. 

So, the correct option is 3 km.

Applications of Ultrasound

• It is used in medical technologies like ‘echocardiography’.
• It is used in the internal mapping of organs.
• It is used to clean parts located in hard-to-reach places, for example, spiral tubes, odd-shaped parts, electronic components, etc.