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Long wave photons

  1. Jan 3, 2006 #1
    Do low energy lightwaves have photons? I assume they do, but is there some way to detect them. I understand high energy light waves pushing around electrons in quantized atomic orbits, but what about radio waves? Photons associated with these wavelengths would be too long to be absorbed by any atoms, so what evidence do we have for the existance of radio wave photons?
  2. jcsd
  3. Jan 3, 2006 #2


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    Light is made of photons, all light, low frequency or high, is photons.

    Turn on your radio. Sound is changed into electricity, and is going from a radio station, to a radio tower, which emits photons, that get to the satellite, and the satellite emits photons that get to your radio, then the radio turns it back from electricity to sound.
    See in the picture that low wavelength radio waves are pretty much completely blocked by the atmosphere, but as on the left side, we can detect them with our satellites.
    Last edited: Jan 3, 2006
  4. Jan 3, 2006 #3
    I understand that. I am not asking for the existance of radio waves, I am asking for proof of the particle nature of radio waves. Light was understood to be a wave, until it was observed to be absorbed and emmited by atoms. Einsteins explanation of the photoelectric effect required quanta, a quality of particles instead of waves. Thus, we now understand light has a wave-particle duality. But the photoelectric effect only works for high energy light. Do we have evidence this wave-particle duality exists in the lower frequencies? i.e. can an antenna absorb only half the energy of a radio wave?
  5. Jan 3, 2006 #4


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    Well, I don't know if individual quanta of radio waves have ever been directly detected (it sounds like an extremely difficult experiment!), but keep in mind that this is all part of a self-consistent picture; that is, quantum mechanics.

    For example, one common type of radio emission in the universe is the 21 cm line of neutral hydrogen. The frequency of this emission (and absorption) line is successfully predicted to high precision by the quantum mechanical model of the hydrogen atom. This model basically says that the emission of these radio photons arises from an energy level transition (specifically, a spin-flip) within the hydrogen atom itself. If the physics of this transition were truly classical, the predicted frequency of radiation would not be the same as observed. In fact, this line is dependent on the very idea of quantized spin states!
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