Question

Explain the use of ultrasonic waves in the measurement of distance of object

Answer 1

Like SONAR: Sonar is consisted of a transmitter and a detector and it is installed in a ship or a boat.
the transmitter produces and transmits ultrasonic waves. these waves travel through water and strike the object an the seabed. on reflection from the objects, the reflected waves are sensed by the detector. the distance of the object, from which ultrasonic waves has been reflected, can be calculated by knowing the speed of sound in water and time interval between transmission and reception of the ultrasound.
Let the speed of sound in water be v and depth of an abject on the seabed be d. Then, total distance travelled by the ultrasonic waves in sea water is 2d. If t be the time between transmission and reception of ultrasound signals, then obviously,

$t = \frac{2d}{v}$
$d = \frac{1}{2} vt$
The above method is called echo ranging.

Answer 2

in the systems like SONAR  when the source of transmittion of waves transmit , the waves travels and strikes the obstacles and come back and recived by the reciver . then the distance traveled by the wares is measured.