"Intensity flicker" of Extremely low frequency (ELF) waves?

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ELF electromagnetic radiation operates within the 3 to 30 Hz range. A hypothetical 3Hz ELF laser pointer paired with a specialized camera could potentially capture the beam's intensity flicker at 3Hz, producing six flashes per second on the viewfinder. However, the camera's limitation of taking only one picture per second restricts precise frequency measurement due to the uncertainty principle, which relates time and frequency resolution. Coherent detection, which is phase-sensitive, may be necessary for accurate measurements, though its application to random events is debated. The discussion highlights the complexities of measuring ELF waves and the implications of coherence in detection methods.
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ELF electromagnetic radiation is in the range of 3 to 30 Hz.

If you had a 3Hz ELF laser pointer and you had a camera that could "see" ELF, would you be able to see the intensity of the beam "flicker" at 3Hz?
 
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The camera could not make more than one picture at a second with a reasonable frequency-sensitivity.
It could directly measure electric fields of a coherent (!) source, then it would simply see the oscillation of electric fields.
 
Why could it not make more than one picture a second?
 
greswd said:
ELF electromagnetic radiation is in the range of 3 to 30 Hz.

If you had a 3Hz ELF laser pointer and you had a camera that could "see" ELF, would you be able to see the intensity of the beam "flicker" at 3Hz?
If the camera detects the instantaneous energy of the incoming wave, it will give 6 flashes per second on the viewfinder.
 
greswd said:
Why could it not make more than one picture a second?
You get the frequency spectrum as Fourier transformation of the time (or space) distribution. If your time range is too small, your frequency range gets large. You can still see "there was something", but you cannot measure the frequency precisely. This can be treated as purely classical effect, but it is closely related to the uncertainty principle in quantum mechanics.
tech99 said:
If the camera detects the instantaneous energy of the incoming wave, it will give 6 flashes per second on the viewfinder.
With coherent light, it will have 6 intensity maxima, yes.
 
Slightly off-topic: Stephen McGreevy did great work- he recorded VLF/ELF events as sound:

http://www.auroralchorus.com/more.htm
http://www.auroralchorus.com/

He uses coherent detection, BTW.
 
Andy Resnick said:
Slightly off-topic: Stephen McGreevy did great work- he recorded VLF/ELF events as sound:

http://www.auroralchorus.com/more.htm
http://www.auroralchorus.com/

He uses coherent detection, BTW.
I would question whether coherent detection can be applied to random events. I am guessing what is meant is direct conversion to zero IF.
 
tech99 said:
I would question whether coherent detection can be applied to random events. I am guessing what is meant is direct conversion to zero IF.

By 'coherent detection', I mean phase-sensitive as opposed to intensity only.
 

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