# Tag Info

## Hot answers tagged virtual-photons

6

Virtual photon clouds are responsible for potentials, not electric and magnetic fields, and this is what makes the explanation of forces in terms of photon exchange somewhat difficult for a newcomer. The photon propagation is not gauge invariant, and the Feynman gauge is the usual one for getting the forces to come out from particle exchange. In another ...

5

Imagine an elastic collision of two protons - something that they also see at the LHC but it's not the most interesting kind of interaction. The two protons will repel because of the electromagnetic interaction. Assume that the distance between them is never too small, relatively to the proton radius. But you may calculate the cross section of this process ...

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You have to realize that when we are speaking of photons, we are speaking of elementary particles and their interactions are dominated by quantum mechanics, not classical mechanics, and in addition special relativity is necessary to calculate anything about them. In general, we know about elementary particles because we observe their traces in detectors for ...

4

I will address the premise that the electron is in an orbit around the hydrogen atom. This is a classical picture overlayed on the basic quantum mechanical one. The electron around the hydrogen atom is in a "spherical" probability cloud about the proton. The above is the n=1,l=0,m=0 probability distribution, which is the lowest energy state. A single ...

4

the wave function of a single photon has several components - much like the components of the Dirac field (or Dirac wave function) - and this wave function is pretty much isomorphic to the electromagnetic field, remembering the complexified values of $E$ and $B$ vectors at each point. The probability density that a photon is found at a particular point is ...

4

The space between atoms depends very much on the medium you are talking about. In solids the typical distance between atoms is about the same as the size of the atoms themselves. In everyday gases at room temperature and pressure the distance between molecules is many times their size, and in deep space you can get densities as low as one proton per cubic ...

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Your seemingly unrealistic gedanken experiment is in fact a quite realistic. First, one can kick out the proton with help of a fast neutron. Next, to increase your "delay" time, you can consider a Rydberg atom with a high enough $n$, so the electron velocity is rather small with respect to the light (and the maximum proton) velocity. What happens to the ...

3

I do not think that this question has an answer. A photon is a quantum mechanical object. a) there is no conservation of photons, virtual or not. b)there is no lower limit to the energy of the photons, so in principle they are infinite ( infrared problem) c)The energy of the virtual photons will depend on the motion of the charge and or the probe that ...

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Apparently you imagine a charge as a point with a Coulomb field around it. Outside the charge there is no charge but there is a field, you say, and it consists of virtual photons. So how many of them are at the distance $r$ from the charge? I let the others answer this question and here I will give you my vision of that. The charge is not point-like but ...

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Unboundedly many, because photon number is not conserved. Every time you push an electron with a classical field, you produce infinitely many soft-photons (if the universe is flat at infinity) and conversely, any long range field which pushes the electron has infinitely many soft-photons getting absorbed in a sense, although you can't tell photons apart, so ...

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It would be useful if your profile gave an indication of educational background in physics or even of age. I would recommend browsing through the CERN teaching resources. How many photons can an electron absorb and why ? Reminds of "how many angels can dance on the tip of a needle". :) If you read the links provided you will understand that an ...

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In your case it is a near field that stands for "virtual" photons. The near field does not propagate like EMW in the sense it is "attached to the charges and currents. In fact, it is the Coulomb and quasi-static magnetic interactions of charges and currents. Despite being time-dependent, the near field decays with distance differently (faster) and does not ...

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There is a difference between the value of a field, and the excitations of that field. If you have a speherically symmetric charge distribution collapse to a black hole (while maintaining the spherical symmetry), there is no electric nor gravitational radiation--Gauss's Law and Birkhoff's Theorem work in tandem to keep the gravitational and electric forces ...

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In QED, for transverse photons, the electric field doesn't commute with the photon number operator. Neither does the magnetic field. In fact, the electric and magnetic fields don't even commute with each other. To get a state with a fixed electric field — or at least with a small uncertainty in it in the quantum sense — we need a superposition of ...

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