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:

i) A strong beam of ultrasonic waves is sent from a transmitter mounted on the ship.

ii) The beam is reflected from the seabed and is received by an under-water detector which is also mounted on the ship.

iii) The time interval between transmission and reception of the ultrasonic signal is noted.