Question

how the method of echo-ranging is used to determine the depth of the sea

Answer 1

The word SONAR Stands for Sound Navigation And Ranging.
SONAR is an apparatus used to find depth of sea or locate under water things like shoals of fish, sunken ships etc.
Working procedure:
SONAR consist of two parts 1) a transmitter for emitting ultrasonic waves and 2) receiver for detecting ultrasonic waves.
Transmitter sends high frequency sound waves of about 50,000 Hz.This pulse wave travels down to bottom of sea.on striking bottom of sea , it gets reflected BaCk to ship in the form of echo. This echo produces an electrical signal in the receiver part of SONAR device.The SONAR measures the time taken by ultrasound wave to travel from ship to bottom of sea.
Speed = 2 ×distance / TIME (Because of echo).
As we know speed of sound in water is nearly 1500m/ s
We can calculate depth by
Depth = speed x time/ 2
THIS method of finding distance is also called as echo ranging.
Marine geologists use this method to determine depth of sea and locate under water hills and valleys.

Answer 2

Sound Navigation And Ranging: A transmitter producing ultrasonic waves is fitted at the bottom of a ship or a boat. The ultrasound waves emitted by the transmitter go to the bottom of the sea and get reflected from the bottom. These are received back by a detector also fitted at the bottom. Knowing the time elapsing between sending and receiving back of the ultrasonic waves and the speed of these waves in water, the depth of sea can be calculated.