| Radar guns are used to detect speeding motorists. Here, a gun transmits waves at a given frequency (shown in blue) toward an oncoming car. Reflected waves (shown in red) return to the gun at a different frequency, depending on how fast the car being tracked is moving. A device in the gun compares the transmission frequency to the received frequency to determine the speed of the car. In this case, the high frequency of the reflected waves indicates the motorist in the red car is speeding and is probably about to receive a ticket. |
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