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B Can photons act as medium for sound?

  1. Mar 22, 2017 #1
    can light collectively or individual photons act as a medium for propagation of sound waves?
     
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  3. Mar 22, 2017 #2

    DrClaude

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    No. For one thing, photons do not collide with each other.
     
  4. Mar 22, 2017 #3

    mfb

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    Not frequent enough to transmit sound, but sometimes they do collide.
     
  5. Mar 22, 2017 #4

    sophiecentaur

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    It's not clear what the context of this question is. It is certainly possible to use a powerful, modulated light beam to vary the temperature in a gas at a high rate, which could manifest itself as an audible pulse as the gas expands. But i don't know of a system that actually uses the effect to 'transmit' an audio signal and directly produce sound without some intermediate form of transducer.
     
  6. Mar 22, 2017 #5
    Ever listened to a radio?
     
  7. Mar 22, 2017 #6
    I don't think that radio waves change the temperature t transmit sound
     
  8. Mar 22, 2017 #7

    davenn

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    no! that is not correct ... not in the context of the OP's question
     
  9. Mar 22, 2017 #8

    sophiecentaur

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    If you focus a powerful case beam onto a small volume, it will raise the temperature fast and that can be audible. It is very hard to produce heating of air with focussed radio waves as the losses are too low to provide enough energy.
     
  10. Mar 22, 2017 #9
    What about lightning.
     
  11. Mar 22, 2017 #10

    sophiecentaur

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    That would be electrical heating - not optical.
     
  12. Mar 22, 2017 #11
    The lightning isn't carrying any information that represents a sound.
    The thunder is a shockwave resulting from rapidly heated air, and is a mix of random frequencies.
     
    Last edited: Mar 22, 2017
  13. Mar 22, 2017 #12

    Vanadium 50

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    I am not sure this works, even in theory. Gas molecules trying to occupy the same space collide every time. Photons passing near each other interact a fraction of the time proportional to E6. That means the most energetic photons tend to interact more, and thus lose energy. In such a dissiptaive medium, the solutions to your wave equation are not sine and cosine, but rather sinh and cosh. I don't think you get sound waves. Or even waves.
     
  14. Mar 22, 2017 #13

    mfb

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    If this discussion continues I'll split it out. It is interesting, but not (B) level.
    There has to be some equilibrium, especially if we ignore processes that change the number of photons.
    I don't know how a region of higher density would propagate if we have a photon gas much larger than the mean interaction length.
     
  15. Mar 23, 2017 #14

    LURCH

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    Don't know if this is what the OP was asking, but in laser serveilance, a laser is bounced off the window of a room, and into a receiver. Any sound waves in the room will cause the laser to vibrate. These vibrations can be measured by the receiver, and converted into sound over a speaker. Of course, the vibrations in the beam are not sounds per se, but the laser could be described as "a medium" that carries the sound from the room to the receiver.
     
  16. Mar 23, 2017 #15

    CWatters

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    Not quite what the OP meant but... some decades ago there was a project in one of the electronics magazines that used a modulated beam of light (pair of torches) to send voice between two houses. Think it was intended as a kids toy.
     
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