Quote:
Originally Posted by shreddr
the speed of light is 186,000 miles per SECOND! so how fast do you think it takes for a laser beam to leave a laser detector and then come back to give the reading? assume a LEO can use it 1/2 mile out, which means the laser beam will have to go 1 mile, so divide that 1 second by 186,000 which is 5 microseconds (millionths of a second) that is the reaction time you need to beat. I am guessing the detector response is probably slower than that.  |
Well, technically, any speed measuring device needs to send multiple pulses to gather the information necessary to calculate a speed. An "instantaneous" reading is only good for a position determination; it takes a differential of position with respect to time to actually calculate speed, and in a speed gun's case, this happens by way of doppler shift.
The flip-side, of course, is that RADAR waves travel just as fast as LASER beams do (all radio waves travel at the speed of light), they just lack the precision and "instant-on" reliability that a LASER has.
In any case, LASER detectors are just there to let you know when it's your turn to pull over.