Question

Which description best explains how a Doppler radar system works?

Answer 1

Answer : (A) "It reflects waves off of objects, measuring the difference of the waves it sends and receives".

Explanation :

In Doppler radar system, radio waves emitted from an antenna. It gives information about the motion of targets and their position.

Phase change between a transmitted wave and received echo is calculated using Doppler radar system.

It also gives radial velocity i.e. velocity in the direction of radar. If the phase shift is positive this means the motion is toward the radar and if the phase is negative this implies the motion is away from the radar.

So, the correct option is (A) "It reflects waves off of objects, measuring the difference of the waves it sends and receives".

Answer 2

A Doppler radar system transmits radio waves off of objects
and receives what bounces back. 

The system measures the difference between the frequency
of the waves it sends and the frequency of the waves it receives.

If the waves come back at a higher frequency than they were sent,
that means the object is moving toward the radar antenna.

If the waves come back at a lower frequency than they were sent,
that means the object is moving away from the radar antenna.

This is kind of what choice-A is trying to say.