Question

Briefly explain about echo in army field

Answer 1

   Ultrasonic waves having frequency higher than that of audible sound waves are produced. They hit an obstruction and return back to the transmission location. The round trip times are noted. The delay in reception gives the exact distance traveled by sound waves.  Thus echo of sound is used here.

   The above concept is used by army, and navy.

Answer 2

same question again and again