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Maximum wavelength of EM

  1. Aug 29, 2010 #1
    Is there any lower limit on the frequency of electromagnetic radiation? I imagine that beyond a certain frequency it becomes impossible to detect, but is there anything in the maxwell equations that establishes a maximum wavelength (besides the limits of the size of the universe)?
  2. jcsd
  3. Aug 29, 2010 #2
    I'm pretty sure there isn't any constraint on how low the frequency can get, numerous theories do make some upper limits though.

    As an aside, I'm not sure what effect even the finite size of the universe would have because of weird boundary conditions, and other cosmology stuff... I don't think any theory could accurately tell you the properties/details of wavelengths comparable to that of the universe; can anybody affirm/deny that?
  4. Aug 29, 2010 #3
    Classically, the longest EM wave simply corresponds to a static electric field, such as point charge that is fixed in space. There is no classical limit to how slowly you can make it move (a body at rest tends to stay at rest).

    Considering quantum theory and the uncertainty of known energy though, the answer is less obvious.
  5. Aug 30, 2010 #4
    Several "popular" and more technical books I've read point out that there is no lower limit. The photon can have arbitrarily small energy, which means that the symmetry it embodies is perfect and unbroken. Because the photon has no rest mass, it can have an arbitrarily small energy.
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