See my earlier query at: http://answers.yahoo.com/question/index;…
What if relatively, they don't have mass? Am I confusing relativism with relativity?
What if relatively, they don't have mass? Am I confusing relativism with relativity?
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They have zero REST mass, so they can travel at c. However, since they travel at such high speeds, they have RELATIVISTIC mass which is proportional to their wavelength.
Light also has momentum by the relation
p = E / c
Light also has momentum by the relation
p = E / c
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Photons have no rest mass. Their momentum (wavelength / energy / polarization) is a function of the emitting process, and the detecting process, not truly part of the photon at all. About the only thing that belongs to the photon is "quantum spin".
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Bull, there is conservation of momentum with the emitting electron when photons are emitted, but they have their own momenta that belongs to the photons itself. That P = hf/c comes from nowhere except the frequency of the photons, which belongs to that photon.
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You answered your own question. Clearly they have no rest mass.
But they do have inertia. And that's found from Mc^2 = hf so that M = hf/c^2 where h is Planck's Constant and f is the photon's frequency. Note that E = hf is the photon's energy. So Mc^2 is the total energy of each photon with relativistic inertia M.
Because they have inertia, one would expect photons to have momentum, even though they have no rest mass. And they do.. P = Mc = hf/c is the photon's momentum expressed in terms of its frequency. That they have momentum has been validated in labs and in engineering. In fact, a lot of laser applications rely on the momenta of photons to do their work.
Yet they have no rest mass...weird, don't you think?
But they do have inertia. And that's found from Mc^2 = hf so that M = hf/c^2 where h is Planck's Constant and f is the photon's frequency. Note that E = hf is the photon's energy. So Mc^2 is the total energy of each photon with relativistic inertia M.
Because they have inertia, one would expect photons to have momentum, even though they have no rest mass. And they do.. P = Mc = hf/c is the photon's momentum expressed in terms of its frequency. That they have momentum has been validated in labs and in engineering. In fact, a lot of laser applications rely on the momenta of photons to do their work.
Yet they have no rest mass...weird, don't you think?