Tagged Questions
3
votes
1answer
59 views
What are the limits of applicability of Coulomb's Law?
Coulomb's law is formally parallel to Newton's Law of Universal Gravitation, which is known to give way to General Relativity for very large masses. Does Coulomb's Law have any similar limits of ...
10
votes
3answers
262 views
Can the path of a charged particle under the influence of a magnetic field be considered piecewise linear?
Ordinarily we consider the path of a charged particle under the influence of a magnetic field to be curved. However, in order for the trajectory of the particle to change, it must emit a photon. ...
0
votes
2answers
95 views
Field energy of/from virtual Photons
I have a slightly out-of line question:
Consider a single electron (or it's current if you please)
The EM field surrounding it will (no doubt) have an EM field energy (T) to go with.
The standard ...
2
votes
2answers
154 views
Where does the mass term come from in the Proca Lagrangian?
There are many good books describing how to construct the Lagrangian for an electromagnetic field in a medium.
$$
\mathcal{L}~=~-\frac{1}{16\pi}F^{\mu\nu}F_{\mu\nu}-\frac{1}{c}j^{\nu}A_{\nu}
$$
...
5
votes
1answer
78 views
Is diffraction affected by interaction between photons and electrons?
Suppose we take a sheet of ordinary metal, make a narrow slit in it, and shine a light beam through the slit onto a screen. The light beam will diffract from the edges of the slit and spread out onto ...
0
votes
2answers
272 views
Can electromagnetic fields be used to deconstruct and reconstruct atoms?
I was thinking one day and came up with a theory after reading about how scientists were studying anti-matter by using electro magnetic fields to separate matter from the anti-matter they made. It ...
4
votes
2answers
168 views
Why possibility for X-ray to excite inner electrons higher than outer electrons?
It seems X-ray absorption spectroscopy is usually ascribed to the interation between photons and inner electrons. Does it mean inner electrons are much preferred by X-ray photons to outer electrons? ...
4
votes
1answer
150 views
Stability of a rotating ring of multiple electrons at relativistic speeds
There was a time when physicists where concerned about electron internal structure. The rotating ring model was one of the proposals to explain how a charge density could become stable against ...
6
votes
1answer
254 views
Is there a strong force analog to magnetic fields?
In special relativity, magnetism can be re-interpreted as an aspect of how electric charges interact when viewed from different inertial frames.
Color charge is more complex than electric charge, but ...
2
votes
3answers
275 views
If electromagnetic fields give charge to particles, do photons carry charge?
As I understand these two statements:
An electromagnetic field gives particles charge
A photon is a quantum of electromagnetic field
It must mean that a photon carries charge. But I guess it isn't ...
2
votes
0answers
292 views
Maxwell's equations in microscopic and macroscopic forms, and quantization
The macroscopic Maxwell's equations can be put in terms of differential forms as
$$\mathrm{d}\mathrm{F}=0,\quad\delta \mathrm{D}=j\implies \delta j=0,\quad \mathrm{D}=\mathrm{F}+\mathrm{P}.$$
...
4
votes
1answer
114 views
Do composite particles that are electrically neutral but have charged constituents radiate?
For example an electron radiates when accelerated. So does a positron. But is the radiation emitted by accelerated positronium the sum of the radiation emitted by each separately? If not, why not? If ...
2
votes
1answer
318 views
is space infinitely divisible?
As a child I remember hearing the popular paradox presented by Zeno proposing that Achilles could never catch a tortoise in a race since he would have to traverse the infinite space between himself ...
3
votes
2answers
272 views
Is there any idea why the electric charges of electron and muon are equal?
Is there any idea explaining why the electric charges of electron and muon are equal?
Edit:
The total charge of a particle is proportional to the integral of its own electric field flow through the ...
2
votes
1answer
142 views
For someone who only studied electromagnetism, what is the modern way to explain electromagnetic fields?
After reading most of the electromagnetism chapters of Feynman's lectures on physics, I would like to understand in more detail, at least an idea, of what causes the electromagnetic fields. Not sure ...
5
votes
2answers
287 views
On Electromagnetic Self Energy
In the process of pair annihilation an electron and a positron annihilate each other to produce a pair of photons, conserving momentum and energy. As the oppositely charged particles approach each ...
8
votes
1answer
193 views
Effect of introducing magnetic charge on use of vector potential
It is well known that Maxwell equations can be made symmetric w.r.t. $E$ and $B$ by introducing non-zero magnetic charge density/flux.
In this case we have $div B = \rho_m$, where $\rho_m$ is a ...
4
votes
2answers
588 views
What's the relation between virtual photons and electromagnetic potentials?
Given that:
1) virtual photons mediate the electric and magnetic force fields
2) the magnetic field is the curl of the magnetic vector potential
3) the electric field is the negative gradient of ...
2
votes
2answers
417 views
What is the physical process (if any) behind magnetic attraction?
I understand that the electromagnetic force can be described as the exchange of virtual photons. I also understand that it's possible for virtual photons, unlike their real counterparts, to have mass ...
8
votes
2answers
320 views
Quantizing EM field
Why when we quantize EM field, whe quantize the vector potential $A^\mu$ obtaining vectorial particles (photons) like the elastic field (phonons) and we can't quantize directly the EM-field tensor ...
1
vote
4answers
396 views
Are electromagnetic “plane” waves measurable or just a virtual concept?
I find plane waves are uncompatible with light cone.
Perhaps plane waves are "virtual" and can never be measured
in that case, shouldn't we call plane waves as "virtual plane waves"?
(other option ...
5
votes
1answer
193 views
Is it true that the angular momentum of electromagnetic waves in an anisotropic medium is an integral of motion?
Extending my previous question Angular moment and EM wave, does it make sense to talk about the angular momentum of electromagnetic waves in an anisotropic medium? It is not obvious that the angular ...
2
votes
3answers
317 views
What is the density of virtual photons around a unit charge?
It seems that virtual photons also exist in vacuum. So the precise question is:
What is the additional virtual photon density due to the electric field of a unit charge?
Or: How many virtual photons ...
6
votes
4answers
796 views
How does charge work if photons are neutral?
How can an electron distinguish between another electron and a positron? They use photons as exchange particles and photons are neutral, so how does it know to repel or attract?
