CBSE Class 9 Answered

SONAR stands for sound navigation and ranging  .

• SONAR is an acoustic device that is installed in ships to measure depth, direction, and speed of underwater objects such as icebergs, sea rocks, shipwrecks, spy submarines, etc.

• It uses high frequency ultrasound for this purpose and works on the principle of echo. It consists of two main devices called transducer and detector. 

• Transducer produces and transmits ultrasonic sound and detector receives the ultrasound that is reflected from the bottom of a sea or an underwater object. SONAR measures the echo of the ultrasound and calculates the depth or distance of underwater objects using the relation,

• These are of two types of SONAR. One is passive, which only detects the incoming. Another one is active SONAR which transmits sound pulses and detects the reflected echoes to detect presence of other sea vessels.

Principle behind SONAR is reflection of sound (Echo).

The sound sent is reflected back from the sea bed which is known as echo.

Let the depth of the ocean be D.

For perpendicular focusing of the sonar

V = 2D/t

=>D = Vt/2

Where V = speed of sound in water

t = time after the echo is detected.

Thus, depth of the ocean can be evaluated.