SONAR : “Sound Navigation and Ranging.” It is based on the principle of ECHO.
ultra- sonic waves are sent in all directions from the ship and then are received on their return after reflection. Using the formula an obstacle such as enemy submarine, ice berg, a sunken ship etc. The time interval between sending and receiving of wave is noted. The distance (depth) can be calculated by vis speed of ultrasonic waves in water. v = 2d/t or d = Vt/2.
