How SONAR, RADAR and LASER can be used to measure distance?



These methods are basically based upon reflection (echo) method. In this method a beam is put on a target which reflects it.
SONAR—It is the short form of Sound Navigation and Ranging. This method generally employs ultrasonic waves. These waves are beamed to a target in water which reflects them back.
RADAR—It is the short form of Radio Detection and Ranging. Radiowaves are beamed in air with the help of the transmitter of the radar. In case an aeroplane comes in their way, they are reflected back. The receiver of radar detects them. Velocity of radiowaves is taken as 3 x ${{10}^{8}}$ m/s and time is noted between sending and receiving the radiowaves, then

LASER—It is the short form for Light Amplification by Stimulated Emission of Radiations. Laser is a very strong beam of one colour and one direction. Large distances like moon from earth can be measured by echo-method using laser beam, i.e., laser is beamed on moon and the reflected beam is received back
By s=vxt/2
where v is velocity of laser and t is
the duration between sending and receiving of the beam. Generally v is taken as the velocity of light in vacuum.