What is a Speed gun?

About Speed gun:

• It is a device to measure the speed of a moving object without having to be in contact with the object.
• To achieve this, the device bounces electromagnetic radiation of a specific frequency off the object, capturing the reflection and using the Doppler effect to infer the object’s speed.
• Speed guns are electronic, and use complex circuitry to emit the radiation used to make the measurement.
• The speed gun was originally developed during World War II for military use and applies the effect using radio waves rather than sound waves.
• How does it works?
  • A speed gun has a radio transmitter and a receiver.
  • The transmitter emits radio waves, which the person holding the speed gun can direct at an object. The receiver collects the waves reflected by the object back in the direction of the speed gun.
  • If the object is approaching the speed gun, the frequency of the returning waves will be slightly higher than that of the transmitted waves. A simple computer in the gun can deduce the object’s speed based on this difference.
• How are the speed and the effect linked?
  • All electromagnetic waves have a fixed speed — equal to the speed of light in that medium.
  • In vacuum, this value is denoted c: 299,792,458 m/s. Any change in the frequency the speed gun detects directly corresponds to the Doppler shift caused by the object’s motion.
  • This principle is powerful because it allows the speed gun to work accurately over a wide range of distances and velocities without being affected by air resistance.
  • A speed gun can calculate the speed of a moving object by multiplying the difference (between received and emitted frequencies) with c and dividing by the emitted frequency times 2.
  • This relationship shows how the difference is directly proportional to the speed of the object: the faster it moves, the more pronounced the difference will be. 
• Uses: It is widely used by law enforcement officials to monitor traffic speed, by coaches to gauge the performance of their athletes, and in various other industries in need of accurate motion tracking.

Q1: What is the Doppler Effect?

It was first described (1842) by Austrian physicist Christian Doppler. It is the apparent difference between the frequency at which sound or light waves leave a source and that at which they reach an observer, caused by the relative motion of the observer and the wave source.

News: The principle behind the working of a speed gun, used for motion tracking