What is a SONAR? Briefly explain its working principle.

SONAR. The acronym SONAR stands for Sound Navigation and Ranging.

Sonar is a device that uses ultrasonic waves to measure the distance, direction and speed of underwater objects.

Principle. It uses the phenomenon of echoes in determining the sea-depth and locating the presence of under-water objects.

Working. A strong beam of ultrasonic waves is sent from a transmitter mounted on the ship. The beam is reflected from the seabed and is received by an under-water detector which is also mounted on the ship. The time interval between transmission and reception of the ultrasonic signal is noted.

Fig. 12.26. Ultrasound sent by a transmitter and received by a detector.

If ultrasonic waves travel with speed v in sea-water and time t is elapsed between the transmission and reception of the ultrasound signal, then the sea depth will be

The SONAR method is also called echo ranging. This technique is used to determine the depth of the sea and to locate underwater hills, valleys, submarine, icebergs, sunken ship etc.