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All Questions

0
votes
0answers
10 views

Are the microwaves in an ECRIS plane polarized?

Or randomly polarized? Are the photons in phase, like in a laser or maser? What is the theory behind how an electron in an ECRIS responds to a microwave photon?
1
vote
1answer
81 views

Is this a correct argument why $c$ is the cosmic speed limit, and what does it mean for the speed of massless particles? [closed]

I am now in my second bachelor, taking both an electrodynamics and a quantum mechanics course. This made me think of an argument to explain why particles cannot exceed the speed of light. So far I ...
6
votes
5answers
365 views

Does classical electromagnetism really predict the instability of atoms?

I will try to give a concise summary of what I wrote below. I understand that it is very long and apologize if I am wasting your time. I used the Liénard-Wiechert potential and the Lorentz force ...
3
votes
3answers
220 views

Systematic expansion of $e^{i\vec{k}\cdot\vec{r}}$ in atomic physics in terms of Legendre polynomials and identifying different $l$ terms

In the context of light-matter interaction one often makes the approximation $e^{i\vec{k}\cdot\vec{r}}\approx 1$. Keeping higher order terms in $e^{i\vec{k}\cdot\vec{r}}$ give magnetic dipole, ...
4
votes
3answers
196 views

How does the Schrödinger model of the hydrogen atom take into account radiation friction?

When one first encounters quantum mechanics, he learns about Bohr's model of the hydrogen atom and one of his biggest problems - electrons were accelerating and not emitting EM radiation (which is ...
-3
votes
1answer
138 views

Classical analog of Bell QM experiment correlation coefficient calculation

This question is motivated by recent experiments in QM entanglement.[1][2] consider the following "simple/ simplified" classical analog of Bells experiment. it has a laser, a standard beamsplitter ...
2
votes
3answers
198 views

Why polarization filter do not dim the light completely?

In a circle there's infinite amount of degrees (eg. 0 deg, 0.00000000000...1 deg etc.) In a ground school we are thought that there's 360 degrees in a circle. A landscape behind my window is ...
8
votes
2answers
261 views

What was Dirac's motivation to study hypothetical magnetic monopoles?

The equation $$\boldsymbol{\nabla}\cdot\textbf{B}(\textbf{r})=0\tag{1} $$ dictates that there can be no isolated magetic monopole. What was then the motivation for Dirac to consider the consequences ...
0
votes
2answers
142 views

Which magnetic field is involved in spin-orbit interaction?

In spin orbit interaction, a magnetic field (internal ,I guess)comes into picture. So how this magnetic field is produced and by who - electron or nucleus? In my book, it says electric field is ...
9
votes
1answer
682 views

The spin-orbit interaction for a classical magnetic dipole moving in an electric field

Spin-orbit coupling is one component of the fine structure of atoms, which is explicitly concerned with the interaction of the electrons' spin with their orbital angular momentum. It can be explicitly ...
4
votes
1answer
2k views

Meaning of dipole approximation for selection rules

This is a really tough one: I would like to understand what it really means to apply the dipole approximation when deriving the selection rules. This question is purely about intuitive understanding ...
1
vote
0answers
63 views

Quantum mechanical/QFT approach to Bremsstrahlung

The problems of damping force or Abraham-Lorentz force should, according to wikipedia, be solved in quantum mechanics or its relativistic counterpart, the quantum field theory. My question is, since ...
1
vote
1answer
589 views

What is the classical equation of motion of spinning magnetic dipole in a magnetic field?

In short: what is the classical equation of motion of spinning magnetic dipole in a magnetic field? I can't seem to find this information...
1
vote
0answers
108 views

Fine Structure and Fine Structure Constant - intuitive relation?

How does the fine structure and fine structure constant relate to each other, intuitively? I've seen $\alpha$ extrapolated as a term in energy calculations for fine structure, but is there a ...
2
votes
5answers
514 views

The relation between frequency and energy of EM waves

In quantum theory, $$E=\hbar \omega.$$ In classical theory, we have the Poynting vector: $$\vec{S}=\frac{1}{\mu_0}\vec{E}_0\times\vec{B}_0\cos^2(kr-\omega t).$$ Given that $S$ is the energy flux ...
0
votes
2answers
3k views

Electromagnetic wave and quantum mechanics [duplicate]

I'm very new to physics. I studied and read about quantum mechanics and what the assumptions are (wave particle duality, uncertainty principle, observation, wave function collapse, etc.), but I also ...
11
votes
2answers
7k views

What are the dimensions, width and length, of a photon?

Everyone is always talking about photon's wavelength. But what about its dimensions? What is length and width of it? And does it even have a point to think about such things? Or those dimensions are ...
15
votes
2answers
2k views

Trouble understanding the Bohr model of the atom

In this article it says: The electrons can only orbit stably, without radiating, in certain orbits (called by Bohr the "stationary orbits") at a certain discrete set of distances from the nucleus. ...
1
vote
4answers
646 views

Excitons in metals-do they exist?

Recently I red an article "Surface Enhanced Fluorescence". It is a topical review by Emmanuel Fort and Samuel Gresillon. Here it is: http://turroserver.chem.columbia.edu/surfaceplasmons/pdf/...
2
votes
1answer
154 views

Angular momenta of photon

$A^\mu$ can have multipole expansions in classical electrodynamics. This gives rise to dipole photon, quadrupole photon etc. For dipole photon $j=1$ (In electrodynamics books they write it as $l=1$). ...
6
votes
3answers
1k views

How is the classical EM field modeled in quantum mechanics?

On the one hand, classical electromagnetism tells us that light is a propagating wave in the electromagnetic field, caused by accelerating charges. Then comes quantum mechanics and says that light ...
5
votes
1answer
596 views

Did the Goudsmit-Uhlenbeck analysis of spin consider relativity?

It's frequently mentioned in introductory quantum mechanics texts that Goudsmit and Uhlenbeck conjectured that the magnetic moment of an electron was due to angular momentum arising from the electron ...
5
votes
1answer
142 views

Classical EM neglects electron recoil?

Imagine two electrons $A$ and $B$ at rest. Electron $B$ is at a vertical distance $r$ above electron $A$. Let us assume that the electrons are constrained to move on horizontal rails. At time $t=0$ ...
-2
votes
1answer
14k views

What causes electron to orbit the nucleus in an atom? [closed]

What causes the electron to orbit the nucleus? Which is the force that causes it to do so? Is it related to the Electro - Magnetic force? .
4
votes
4answers
3k views

Why are the classical electron radius, the Bohr radius and the Compton wavelength of an electron related to each other?

Using the definition of the fine-structure constant $\alpha = \frac{4 \pi \epsilon_0 \hbar c}{e^2}$ and the Compton wavelength of an electron $\lambda_c = \frac{h}{m_e c}$ the classical electron ...
4
votes
1answer
710 views

Classical (or semi-classical) interpretation of photoelectric effect?

This site says that "it has recently been proven that the photoelectric effect can be interpreted classically (or at least semi-classically) in non-particle, wavelike terms". Is anyone familiar with ...
1
vote
4answers
593 views

Interaction of matter with EM fields

For the interaction between electromagnetic fields and matter, when do we have to include quantization of the EM field and when we can ignore it? when do we have to include quantization of atomic ...
4
votes
1answer
47 views

Connections of iterative solvers for large systems of equation in Physics?

I am trying to find the domains in physics where solving large systems of equations is computationally expensive. The sparse systems are of my particular interest, where the input matrix A is in GBs (...