2023-12-18 23:00:00
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Have you ever wondered how it is possible that a device as small and simple as a radar can be able to so accurately capture the speed of your car when you pass by it? And think, on many occasions these speeds can even exceed 120 km/h, which makes them very hard to track with precision. However, radars appear to be incredibly accurate technologies, capable of easily detecting the movement of any object or, in this case, vehicle.
How do they do that? Well thanks to Doppler effect, a physical phenomenon that allows any technological device that implements it to be capable of capturing the vehicle return echoes in question, thus being able to measure its radial velocity. We tell you what exactly this curious effect consists of and how it is normally applied to speed cameras.
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THE DOPPLER EFFECT
This phenomenon that defines the operation of radars, the Doppler effect, owes its name to its discoverer. Christian Doppler, who first observed in 1842 the curious interaction between waves when changes in frequency appear. For an individual who is in a space where the Doppler effect is occurring, this alteration in frequency can be perceived as a small increase or decrease in hue of a sound or a light, depending on the type of wave that acts as the protagonist.
In itself, it is a phenomenon based on the relationship between the relative speed of a source, in this case, a vehicle, and the observer, the radar in the case we are discussing. That way, when the source and the observer get closer, the frequency received by the radar is higherwhile when they move away, the apparent frequency decreases.
Charly Whisky
Representation of how waves compress or expand depending on the movement of the source.
Although it may seem complicated to understand, it is not so complicated. In fact, it is an effect that you experience every day without hardly realizing it. Think of a ambulance: when it gets closer, you identify it because its sound is getting louder and louder. sharp; On the contrary, when it moves away, its sound becomes louder. grave as it disappears. This is because as it approaches, the sound waves it emits go away. compressing, increasing the frequency, resulting in a higher, higher pitch. As you move away, the effect is the opposite: the waves expanddecreasing the frequency between them and giving rise to a much deeper tone.
THE DOPPLER EFFECT IN RADARS
Now, in the case of electromagnetic waves – not sound – such as those used in radars, the Doppler effect takes on a very similar form: if an object moves towards the radar, the waves that are reflect they will have a higher frequency, while if you move away, they will have a lower frequency.
And the radars themselves emit electromagnetic waves continuously, being the reflections of their own echoes what they detect. That way, when the waves collide with an objectthese experience a certain change in their characteristics, making it possible to know from them the way in which the object they collided with was moving (including its speed).
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Thus, in a traditional speed radar, it emits waves constantly. When a car passes by you, those waves it emits will collide with the vehicle and reflect. Depending on what the speed of that vehicle has been, the way in which electromagnetic waves are reflected will vary. In this way, depending on how the radar detects the waves again, it will be able to calculate the exact speed of the vehicle and, immediately afterwards, confirm whether it was greater or less than that allowed on that road.
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