Explain the working and application of a sonar.

SONAR is an abbreviation of Sound Navigation and Ranging. It is an acoustic device used in measuring the direction, speed, and depth of under-water objects viz. ship wrecks and submarines using ultrasound.

(i) Sonar consists of a transmitter and a detector and is installed in a boat or a ship.

(Ii) The transmitter produces and transmits ultrasonic waves. These waves travel through water and after striking the object on the seabed, get reflected back and are sensed by the detector.

(iii) The detector converts the ultrasonic waves into electrical signals which are appropriately interpreted.

(iv) The distance of the object that reflected the sound wave can be calculated by knowing the speed of sound in water and the time interval between transmission and reception of the ultrasound.

Let the time interval between transmission and reception of ultrasound signal be t and the speed of sound through seawater be v. The total distance, 2d travelled by the ultrasound is then, \( 2d = v × t \) .

This method of measuring distance is also referred to as echo-ranging.