2007-02-02 04:34:35 · 5 answers · asked by satouqi 3 in Politics & Government ➔ Law Enforcement & Police
Radar can be used to measure the speed of an object, due to a phenomenon called Doppler shift. Like sound waves, radio waves have a certain frequency, the number of oscillations per unit of time. When the radar gun and the car are both standing still, the echo will have the same wave frequency as the original signal. Each part of the signal is reflected when it reaches the car, mirroring the original signal exactly.
But when the car is moving, each part of the radio signal is reflected at a different point in space, which changes the wave pattern. When the car is moving away from the radar gun, the second segment of the signal has to travel a greater distance to reach the car than the first segment of the signal. As you can see in the diagram below, this has the effect of "stretching out" the wave, or lowering its frequency. If the car is moving toward the radar gun, the second segment of the wave travels a shorter distance than the first segment before being reflected. As a result, the peaks and valleys of the wave get squeezed together: The frequency increases. Hows that for some apples!!
2007-02-02 04:44:39 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The radar tells the cop how fast the speeder is going. The cop catches the speeder.
The device is a doppler radar. It tells how fast something is moving towards or away from it by bouncing a radar beam off that object then checking the frequency of the wave that bounces back. It is highly accurate.
2007-02-02 12:36:37 · answer #2 · answered by speakeasy 6 · 0⤊ 0⤋
All three answers above mine are correct.
People think that we sit and wait for the radar to beep and tell us someone is speeding (ie. classic movie moment where the sleeping cop is behind the billboard and the radar goes off). You must observe the vehicle speeding and then confirm the reading with the radar.
2007-02-02 14:21:47 · answer #3 · answered by joeanonymous 6 · 0⤊ 0⤋
this isn't really a question and radar guns don't catch speeders, police do.
2007-02-02 12:37:01 · answer #4 · answered by meathookcook 6 · 1⤊ 0⤋
Actually, I do not need radar/lidar to write you a speeding ticket. I have been trained to observe traffic and determine speed. The radar/lidar only confirm my observation. It is my observation of the speed that will beat you in court, not the radar/lidar.
2007-02-02 13:53:09 · answer #5 · answered by Combatcop 5 · 0⤊ 0⤋