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B How are photons able to carry messages?

  1. Jul 26, 2017 #1
    I'm having trouble understanding how simple particles can be received and then with that information translated into a song on the radio or a program on television. Any help?
     
  2. jcsd
  3. Jul 26, 2017 #2

    Dale

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    Why would you try to use quantum mechanics to analyze something that is perfectly well described with classical mechanics? I would recommend just focusing on Maxwell's equations instead of QM.
     
  4. Jul 26, 2017 #3

    davenn

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    Exactly ... as photons DONT carry messages

    Oscillating voltages in the transmitter are sent to the antenna the antenna then radiates an electromagnetic wave that is picked up by the receiving antenna(s) it is converted back to a voltage that is then demodulated that then produces audio and video ( as in a TV) or just audio for an AM or FM radio station. Or info displayed on your mobile phone or other device


    Dave
     
  5. Jul 26, 2017 #4

    Andrew Mason

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    All information can be reduced to a stream of digital bits -1s and 0s -. And any physical thing that can be streamed between two points can be modulated to make a bit stream, provided there are enough of them. You could transmit pictures using a stream of ping pong balls. But it is simpler and much faster to use photons.

    AM
     
  6. Jul 27, 2017 #5

    davenn

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    I think you missed the point of his mis-understanding ..... reread Dale and my posts :smile:
     
  7. Jul 27, 2017 #6

    sophiecentaur

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    It seems to me that you want too much, too quickly. Your post includes virtually the whole of communications theory and practice.
    You need to go one step at a time. Dave's post gives you a partial list of some of the basic steps in a chain which allow music (or any other varying quantity) can be transmitted from a source to a receiver. Look at each of his steps in turn and formulate a question about it that can be answered.
    You must expect for this to take a long time with many repeats. There will be many mistakes and misunderstands on the way. :smile:
     
  8. Jul 27, 2017 #7

    CWatters

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    Photons can have different energies corresponding to different frequencies. You can vary the energy/frequency to encode the signal.
     
  9. Jul 27, 2017 #8

    Andrew Mason

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    Maybe, but it seems to me that the original poster's difficulty is not with photons per se but with how complex information can be effectively carried by them. An individual photon cannot carry much information but a stream of them certainly can.

    AM
     
  10. Jul 27, 2017 #9

    sophiecentaur

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    It's another demonstration of how people feel pressured to use 'photons' in any explanation of anything. It's as if it makes things more approachable but it's actually quite the opposite.
    The only information that a single photon can carry is the fact that it existed and roughly the time it existed. A series of bursts of photons (a flashing light!!!) can be used to send Morse Code messages. That is easy to appreciate - much easier than the idea of 'digital' TV or sound - but it's a first stab. The brightness of light can be varied by the (analogue) light and dark stripes on the optical audio track on old film and those brightness variations can be used to move a loudspeaker coil to reproduce sound.
    There's no end to it!
     
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