Asonar system measures distance by determining the
a.

density of a body of water.
b.

time it takes for sound to be absorbed.
c.

difference between regular sound waves and ultrasound.
d.

time it takes for sound waves to bounce off a surface.

D.

A sonar System measures distance by determining the time it takes for sound waves to bounce off a surface

Explanation:

SONAR : SOund Navigation And Ranging

Its a device used to locate the position, distance and direction of objects under the surface of water.This device is fitted at the bottom of the ship.

Source : Ultrasonic wave producing object .

Detector : It receives the reflected wave and convert it into electrical signal.

Formula :

Here

d = distance betweeb source and object

2d = total distance from source to detector after reflection of wave

t = total time taken by wave to reach the detector

v = velocity of sound wave

If time is known then 2d can be calculated using formula.

Hence distance can be calculated from time to bounce off the surface