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Highest Possible Frequency of Photon

  1. Feb 20, 2009 #1
    What is the highest possible frequency that a photon can have?

    Here is an answer from Answers.com. Is this correct?
    That's a good question and I've often wondered about it. I think, but I'm not certain, that the answer is the reciprocal of the Planck time, which is 10^43 Hz. At shorter wavelengths than 10^-35 m., which is the wavelength that corresponds to this frequency, the photon would disappear in the quantum foam. A photon with this frequency would have an energy of 10^43 times Planck's constant, 6.67x10^-34 joule-secs. This energy is 6.7x10^9 joules which is nearly 2000 kilowatt hours. Its mass equivalent would be 6.7 x 10^-9/ c^2, which is 8 x 10^-5 gram. Most of the maximum possible quantities are obtained by juggling the fundamental constants of physics; the speed of light c, Newton's universal gravitational constant G, Planck's constant h etc. until you get a quantity with the right dimensions, then work it out numerically with your calculator. For instance if you take the square root of (Gh/(c^3)) you get a quantity with the dimensions of length, which turns out to be the Planck distance, which is the wavelength of this photon; about 10^-35 metre.​

    Last edited by a moderator: Oct 28, 2009
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  3. Nov 10, 2011 #2
    can someone provide answer to this question ? i'm of the opinion that the highest frequency of a photon would be 2 X 1.23558996 × 10^20...any frequency beyond this means, the photons are so tightly coupled that, they form electron-positron pair ?
  4. Nov 10, 2011 #3
    The question is from Feb 2009.

    I'm not positive, but I like the proposed answer:

  5. Nov 10, 2011 #4
    Thought I should check a bit, here is what Wiki says:


    It should also be noted that the measured frequency is frame dependent so you can make it almost any value by changing observer speed. It's also dependent on gravitational potential at the observer.
    I wonder if such a high frequenecy photon, very energetic, leaves a gravity well (say a star for example) what happens to it as it emerges into free space?? I think the best we can answer is the Wiki statement.
    Last edited: Nov 10, 2011
  6. Nov 10, 2011 #5
    i was searching on the net following my post on pf and came across this
    "If the energy in the center of mass system of the two photons is large enough, matter can be created"
    actually, the value how i arrived was, equating e=mc2 = hv. Take mass of electron, one of the fundamental, stable particles and you will arrive at this frequency.
    coincidentally, this frequency is the range of high energy gamma rays !
  7. Nov 10, 2011 #6


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    If you are saying that the highest energy gamma rays are the mass of an electron-positron pair, this is certainly not correct. This is only about 1 MeV, and much higher energy gamma rays are known - at least into the TeV (10^12 eV) region. A single gamma ray cannot decay into an electron-positron pair, because such a decay cannot conserve energy and momentum.
  8. Nov 11, 2011 #7
    Thanks for the clarification..its clear now :)
  9. Nov 11, 2011 #8
    Arguments involving the Planck time are speculative because physics at the Planck scale is completely unknown. It is not even known if the Planck energy value represents anything particularly significant in physics, because no experimental activity at those energies have been performed.

    Based on non-speculative physics, it is unknown if there is such a limit on photon frequencies.
  10. Nov 11, 2011 #9
    The Wiki article on two photon physics is interesting but opaque....never heard of that before, still don't get it....

    anybody have any references/papers that describe whats going on???
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