0
votes
0answers
12 views
How does optical phase modulation produce photons with different frequencies?
The classical description of electro-optic modulators is an index of refraction that depends on the applied voltage. For example, for a sine modulation $\sin(\Omega t)$, a monochromatic laser of ...
10
votes
1answer
180 views
What are the consequences of relativistic angular velocities?
If I take a rod of some radius $r$ and length $L$, and I spin this rod with angular velocity $\omega$. How would the geometry of the rod appear to an observer as one converges to $c$? What are the ...
1
vote
4answers
81 views
How does moving charges produce magnetic field?
I'm tutoring High school students. I've always taught them that:
A charged particle moving without acceleration produces electric as well as magnetic field?
It produces electric field because ...
3
votes
1answer
40 views
Why doesn't this equation for orbital motion change with position in the orbit?
The question and answer are on pg.8-10 of this PDF:
At first, I went through it, thinking nothing of it. But then, I wondered: "What if we picked a final state in which the space junk was NOT at ...
1
vote
1answer
164 views
Finding Electric Field outside a Charged Cylinder
I'm trying to solve a problem that involves finding the electric field due to a uniformly cylinder of radius $r$, length $L$ and total charge $Q$. Well, my thought was: if I am to use Gauss' Law, I'll ...
3
votes
2answers
466 views
Are Colors Emitted at Specific Temperatures?
There are quite a few nagging questions I have been having over the years, I do not require a full explanation, just some guidance in my assumptions and pointers if I am very wrong.
My basic ...
0
votes
1answer
38 views
Relativistic Lagrangian transformations
I need to study the relativistic lagrangian of a free particle.
It's
$\ L= - m c^2 \sqrt[2]{1- \frac{|u|^2}{c^2}} $ I need to study the translation, boost and rotation symmetry. I say it doesn't ...
4
votes
2answers
55 views
How to directly calculate the infinitesimal generator of SU(2)
We commonly investigate the properties of SU(2) on the basis of SO(3). However, I want to directly calculte the infinitesimal generator of SU(2) according to the definition $$X_{i}=\frac{\partial ...
9
votes
1answer
213 views
How is the Dirac adjoint generalized?
I am wondering how one can generalize the Dirac adjoint to flat "spacetimes" of arbitrary dimension and signature. To be more specific, a standard situation would be to consider 4 dimensional ...
0
votes
1answer
22 views
Magnetic engine
Is it possible to mimic crrent engine design (to some extent) by replacing the cylinders with opposed magnets? A device interupts their natural desire to push away from each other allowing them to ...
0
votes
1answer
17 views
Doubt on the analysis of $RC$ circuit
I'm studying $RC$ circuits and I'm in doubt on how to deal with one kind of situation. Well, first when we have simply a circuit with just one resistor and one capacitor in series, or a circuit that ...
-1
votes
0answers
18 views
Electric Field and Electric Potential [closed]
How can electric field and electric potential function for charged conducting and uniformly charged non-conducting spheres?
0
votes
1answer
40 views
Difference between velocity vectors, relative speed
Consider two particles moving in the same direction instantaneously but one of them follows a circular path and one follows a straight path.
If I adopt a rotating frame of reference in which the ...
0
votes
0answers
16 views
UV light penetration into silicon
I'm in need of some information about UV (particularly UVA) light's ability to penetrate into silicon. Specifically, I am looking for a relationship between wavelength and penetration depth. Also, if ...
2
votes
1answer
17 views
Magnetic Force on a Loop and number of turns
Suppose we have a rectangular current-carrying loop with current $i$, then we know that the magnetic force on each side can be found as:
$$F=iL\times B$$
Where $L$ is the vector in the direction of ...
-1
votes
0answers
19 views
The Sine pattern of variation [closed]
I'm trying to fully understand sin and cos as a certain pattern of variation, a particular variation that start's to decelerate smoothly towards the peaks and starts to accelerate abruptly towards the ...
1
vote
2answers
55 views
How & Why does accelerating charges radiate electromagnetic radiation?
Lets consider it case by case:
Case 1: Charge particle is at rest. It has electric field around it. No problem. That is its property.
Case 2: Charge particle started moving (its accelerating). We ...
-4
votes
0answers
17 views
Electric and Magnetic Field [closed]
Accelerated charges directed into regions between parallel plates with E and B fields – how are the charges deflected?
0
votes
1answer
26 views
Wave function interpretation $y(x,t) = (0.35m)\sin(10\pi t-3\pi x + \frac\pi{4})$
Wave function interpretation $y(x,t) = (0.35m)\sin(10\pi t-3\pi x + \frac\pi{4})$
I used to deal with function with one variable
And now theres are two, how can I interpret them?
Is $10\pi$ still ...
7
votes
1answer
86 views
What is the reason that relativistic corrections for hydrogen atom work?
Here I cite part from Sidney Coleman's lectures on Quantum Field Theory:
It is a phenomenal fluke that relativistic kinematic corrections for the Hydrogen atom work. If the Dirac equation is used, ...
3
votes
1answer
88 views
Is electromagnetism a dead research field?
Are there any phenomena, we consider as electromagnetic and have no explanation for ?
3
votes
2answers
38 views
Stable Nuclei - Deviation from equal protons and neutrons
While studying the semi-empirical mass formula for nuclei, I came across an "asymmetry term" whose function, as far as I understand, is to build in the fact that nuclei "prefer" to have equal numbers ...
3
votes
3answers
42 views
Showing Hubble constant is time-independent
I have the following question for homework:
Show that the Hubble constant $H$ is time-independent in a universe in which the only contribution to energy density comes from vacuum energy.
So in ...
3
votes
2answers
104 views
Estimation of the internal electric field strength in the pn-junction
I would like to compare my result in an order of magnitude. So, How can I estimate the strength of the electric field in a typical Si PN-junction?
0
votes
0answers
19 views
Specular intensity [closed]
Im currently studying for an exam and have been going through some past papers on the subject, however i have come across a question that has recursively come up each year and the notes on it are not ...
8
votes
3answers
686 views
Is it possible to reproduce Double-slit experiment by myself at home?
I want to reproduce this experiment by myself. What I need for this. What parameters of slits and laser/another light source it needs? Is it possible to make DIY-detector?
3
votes
3answers
224 views
Why we see upright images?
Since it's convex lens there in our eyes so image formed on our retina is inverted, so how come that we see upright images?
2
votes
1answer
49 views
Field Tensor and classical limits
I would be very grateful if someone would kindly explain this generalization of the Lorentz force law to the special relativity domain. Please bear with me.
Classically, the Lorentz force law is ...
3
votes
1answer
45 views
What is a $TEM_{900}$ cavity radiation mode?
I am reading a paper by Serge Haroche stating the cavity they use sustains a Gaussian mode of the e.m. field called $TEM_{900}$. I understand what Gaussian means. I found this explaining what TEM ...
21
votes
4answers
261 views
An entropy of the Wigner function
Is there an entropy that one can use for the Wigner quasi-probability distribution?
(In the sense of a phase-space probability distribution, not - just von Neumann entropy.)
One cannot simply use ...
1
vote
1answer
48 views
Lie algebra of lorentz group
I'm stuck in following calcualtion from sredniki's QFT book.(Its actually in the solution manual)
How can i get from
$$\delta\omega_{\rho\sigma}(g^{\sigma\mu}M^{\rho\nu} - g^{\rho\nu}M^{\mu\sigma})
...
1
vote
1answer
53 views
What is the coefficient $\mu_\text{air}$?
I am answering some exercises in thermodynamics, and I am still in trouble with some values and constants.
In the exercise, it is given: $\mu_\text{air}=1.8\cdot10^{-5}~\text{kg/m s}$. What for is ...
4
votes
2answers
46 views
Equivalent RC circuit to a RRC circuit?
I'm in doubt about a situation that I've seen sometimes: imagine we have a resistor in parallel with a resistor and a capacitor in series. Since I don't know how to generate figures of circuits to ...
2
votes
2answers
117 views
Why is the temperature zero in the ground state?
This is probably a simple question: I see this claims in many books, but I can't figure a reason why this is true.
So my question is why this claim is true:
"If we know that the system is in the ...
3
votes
1answer
240 views
What is the meaning of the concepts of “operator mixing” (and anomalous dimensions) [closed]
I am looking for an explanation about the idea of "operator mixing" and its associated concept about when anomalous dimension has to be thought of as a matrix.
For example this idea is slightly ...
2
votes
0answers
23 views
How to numerically solve a laser driving semi-classical two-level system using Floquet formalism?
Consider the semi-classical laser driving two-level atom, where the laser is treated classically and the atom is treated quantum mechanically. The effect of laser on the atom is a dipole coupling:
$$
...
-2
votes
1answer
38 views
A double-sided lever and multiple forces [closed]
Assume a double-sided lever where the left arm has a length of a and the right arm has a length of b + c. Please refer to this ...
-3
votes
0answers
19 views
Lowest attenuation at 1550 nm for link lengths in 30-50 km range [closed]
Could someone point me to a reference that features the lowest-possible loss value (as of today) for transmission of light at ~1550 nm? In particular, the typical length of the optical link is in the ...
0
votes
0answers
39 views
How does the volume change affect an adiabatic process?
A gas consisting of rigid diatomic molecules was initially under standard conditions. Then the gas was compressed adiabatically, 5 times the original volume. Find the mean KE of rotating molecules ...
1
vote
2answers
205 views
4 digit Miller Index for a cubic structure?
As the title states, can a Miller index for a cubic structure have 4 digits? If I have a structure with intercepts (2,8,3) on the x-y-z axes respectively, the following Miller index would be (12,3,8), ...
2
votes
1answer
42 views
Is this 2D structure triclinic?
The only rotation axis obvious to me is rotation by 360 degrees, the identity. Vertical mirror planes I've been dicing and cutting it through several planes and I still see none. Yet, the structure ...
0
votes
0answers
24 views
electrostatic repulsion [closed]
Consider a homogeneous ring of radius $R$ made of a thin wire of cross section $A$ with $R^2≫A$. A charge $Q_1=10\mu C$, uniformly distributed over the ring, broke it apart due to electrostatic ...
2
votes
2answers
141 views
Indistinguishable particles in quantum mechanics
If you have two particles of the same species , Quantum mechanics says that $\Phi_{m_{1},x_{1},p_{1},m_{2},x_{2},p_{2}}=\alpha\Phi_{m_{2},x_{2},p_{2},m_{1},x_{1},p_{1}}$
But I don't understand why ...
1
vote
1answer
59 views
Combining two finite number fock spaces into one
Say I have two separate systems of identical Bosons, one with N Bosons the other with M. System one is described by a state $|\psi_1\rangle$ the other with $|\psi_2 \rangle$ which are expressed in a ...
2
votes
0answers
52 views
Categorizing solutions to Hierarchy problem
We know that no gauge symmetry can prevent a term $m_\phi^2|\phi|^2$ for a scalar field, and that, given the quadratic loop corrections, the natural scale is $m_\phi \sim M_P$. This is related to the ...
0
votes
0answers
30 views
Historical aspect of wave theory of light
Huygens thought light as a wave. Wave is a propagation of physical disturbance. We now know that light is electromagnetic field. Electric and magnetic field fluctuates here. What Huygens really ...
0
votes
0answers
38 views
An application of Toeplitz operators
I want to find an application of the Toeplitz operators. All I need is a known problem (not an open problem) which solution use the theory of Toeplitz operators. I don't need all the details but I ...
0
votes
2answers
47 views
Dividing values with units
I'm reading about the subject of heat in a basic physics book. If I am not mistaken the formula to work out how much energy is required to increase the temperature of water is
...
-2
votes
0answers
19 views
Circuits using generators and cells and capacitors [closed]
This question was in a science worksheet we had, the description read as follows:
Tim has designed a generator that uses wind power and provides 9V. He decides to design a circuit using diodes ...
3
votes
3answers
58 views
Does the expansion of the universe soon after the Big Bang affect the amount of time that light takes to reach us?
If faster than light travel is impossible, how is it that light emitted from matter so close together in the time soon after the Big Bang is only now just reaching us? I would assume that there would ...
