Since the mid-1950s, speeding cars have been flagged based on the accurate reading of a radar gun. The police radar gun is designed for accuracy and for ease of use. To ensure proper operation, it is calibrated daily with the help of a tuning fork.
While it is a complex piece of electronics, the underlying principle is quite simple and one which most people have already encountered before.
Waves on a Pond
The idea behind a radar gun is that a radio wave has a frequency, a vehicle will bounce the radio wave back and the frequency is measurable. Radio signals travel in waves. That means if it bounces back, the frequency should be the same as the frequency that emanated from the radar gun.
If the vehicle is moving, the radio waves would also change, and the change can be calculated. The calculated change in radio waves has a direct correlation with the actual speed of the vehicle.
To visualize this, imagine a boat or any object floating on a pond or lake. A person can generate waves which will reach the boat. The waves bounce back upon hitting the boat. If the boat is moving, the frequency of the waves would also change. If it is moving away from the source of the waves, the waves will become elongated. If the boat is moving closer to the source, the waves will be shorter than the original.
The Doppler Effect
Also called the Doppler effect, the Doppler shift is evident with vehicles on the highway. As a car approaches, the sound the car makes changes and pitch becomes higher. After the vehicle has passed, the pitch becomes lower and then fades.
The change in frequency is due to the relative speed of the vehicle to the observer. As it gets closer, the sound waves shorten, resulting in increasing pitch. When the vehicle leaves, the sound waves lengthen, leading to a lower-pitched sound.
There’s no doubt radar guns are helpful in the law enforcement sector other than sports. As far as accuracy and reliability are concerned, the Government is likely to keep investing in these useful devices.