### Theory:

(a) Speed of an automobile:

A source attached to a police car emits an electromagnetic wave. A moving vehicle, which acts as a moving source, reflects the wave. The reflected wave's frequency has shifted. The car's speed can be calculated using the frequency shift. This change in frequency aids in the detection of speeding vehicles.

Measuring the speed of moving vehicles

A radio transmitter and receiver are used in radar speed guns. They send out a narrow radio signal, then receive the same signal after it bounces off the target object. If an object moves toward or away from the gun, the frequency of the reflected radio waves changes, and the speed of the vehicle can be calculated using the Doppler equation.

(b) Tracking a satellite:

As a satellite moves away from the Earth, the frequency of radio waves, it emits decreases. The location of satellites is determined by measuring the change in frequency of radio waves.

Determination of satellite's location

Radio waves are sent in RADAR, and the reflected waves are detected by the RADAR station's receiver. The speed and location of aeroplanes and aircraft are tracked using frequency change.

Finding the speed and location of an aircraft using radar(Design)

(d) SONAR:

The velocity of marine animals and submarines can be determined using SONAR by measuring the change in frequency between the sent and received signals. This method is called echo-ranging. Sonar technique is used to determine the depth of the sea and to locate underwater hills, valleys, submarines, icebergs etc.

Finding the seabed distance using SONAR
Reference:
https://commons.wikimedia.org/wiki/File:Gps-atmospheric-efects.png