Question

What is an echo 2 areas of its application

Answer 1

Echo:
When a sound wave is produced in air, some of it is absorbed after hitting with a reflector while some of the sound wave is reflected back to the listener. This reflected sound is called echo.

This technique is also used to find the depth of sea or distance of submarines.
It also helps to estimate the distance or hills and mountains.
This technique is also very helpful in the medical field as well. Doctors used this phenomenon in cardiography, sonogram and many other medical diagnosis. 

Hope it will help you. Thanks.

Answer 2

Echo is the return of sound waves after hitting a rigid surface in the same medium after 0.1 second...
Uses....
1-It helps in detecting the depth of sea by help of SONAR.
2-It helps in detecting the ships and submarine in seas or oceans by help of a RADAR.

Hope it helps (｡’▽’｡)♡