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I am new and so is my interest in quantum mechanics. I am curious to know if all photons have motion? and if a photon is not in motion is it detectable?
I am new and so is my interest in quantum mechanics. I am curious to know if all photons have motion? and if a photon is not in motion is it detectable?
If a photon can only be observed because it is moving, then how would it be possible to know if it were in a non moving state? also, is it assumed that it is always in a moving state or is it a proven fact?
Photons always move at the speed of light (being as they ARE light), approximately 300,000,000 meters per second.
I am new and so is my interest in quantum mechanics. I am curious to know if all photons have motion? and if a photon is not in motion is it detectable?
It is a basic concept of relativity (not quantum physics) that a photon moves at 300,000,000 m/s relative to any frame of reference. And relativity has an enormous number of confirming experiments.If a photon can only be observed because it is moving, then how would it be possible to know if it were in a non moving state? also, is it assumed that it is always in a moving state or is it a proven fact?
The only thing i've heard of in the sense of slowing down photons is that a bunch of scientists manged to slow light down to less than 1mph using some sort frozen phosphorus or something like that, but incase you mean photons in empty space then my anwser is no light always moves at (c)
You can slow light down, but not the individual photons. They still move at c. Even in a medium where the speed of light is less than c. Only in a vacuum is the speed of a lightwave determined by the speed of photons. In a medium it is the properties of that medium that largely determine the speed of lightwaves. The photons are absorbed and re-emitted many times, which causes the 'delay' and slower net speed.
1) Yes, v=c/n, where n > 1 is the medium refraction index.
2) No, it is not since particle velocity is always smaller that c but may be higher than c/n.
Bob.
On the other hand, if a photon has an energy beyond the phonon spectrum, then while it can still cause a disturbance of the lattice ions, the solid cannot sustain this vibration, because the phonon mode isn't available. This is similar to trying to oscillate something at a different frequency than the resonance frequency. So the lattice does not absorb this photon and it is re-emitted but with a very slight delay. This, naively, is the origin of the apparent slowdown of the light speed in the material. The emitted photon may encounter other lattice ions as it makes its way through the material and this accumulate the delay.
From our very own Physics FAQ (post #4):
So, maybe I was wrong that photons are absorbed/emitted by atoms. Rather they are absorbed by the material as a whole, eg the lattice.
So I still believe that photons travel at c, always.