Editing Radar speed gun (section)

===Doppler effect===
Radar speed guns use [[Doppler radar]] to perform speed measurements.

Radar speed guns, like other types of radar, consist of a [[Transmitter|radio transmitter]] and [[Radio receiver|receiver]]. They send out a radio signal in a narrow beam, then receive the same signal back after it bounces off the target object.  Due to a phenomenon called the [[Doppler effect]], if the object is moving toward or away from the gun, the [[frequency]] of the reflected radio waves when they come back is different from the transmitted waves. When the object is approaching the radar, the frequency of the return waves is higher than the transmitted waves; when the object is moving away, the frequency is lower.  From that difference, the radar speed gun can calculate the speed of the object from which the waves have been bounced. This speed is given by the following equation:
:<math>{v}=\frac {\Delta f}{f} \times {\frac {c}{2}}</math>
where <math>c</math> is the [[speed of light]], <math>f</math> is the emitted frequency of the radio waves, and <math>\Delta f</math> is the difference in frequency between the radio waves that are emitted and those received back by the gun. This equation holds precisely only when object speeds are low compared to that of light, but in everyday situations, this is the case and the velocity of an object is directly proportional to this difference in frequency.