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

  1. Dec 2, 2015 #1
    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?
     
  2. jcsd
  3. Dec 2, 2015 #2

    mfb

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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.
     
  4. Dec 2, 2015 #3
    Why could it not make more than one picture a second?
     
  5. Dec 2, 2015 #4

    tech99

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    If the camera detects the instantaneous energy of the incoming wave, it will give 6 flashes per second on the viewfinder.
     
  6. Dec 2, 2015 #5

    mfb

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    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.
    With coherent light, it will have 6 intensity maxima, yes.
     
  7. Dec 2, 2015 #6

    Andy Resnick

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  8. Dec 3, 2015 #7

    tech99

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    I would question whether coherent detection can be applied to random events. I am guessing what is meant is direct conversion to zero IF.
     
  9. Dec 3, 2015 #8

    Andy Resnick

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