Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.
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35 views
MRI's and Electromagnetic Radiation
If the waves in an MRI can go through our body, why is it that light with its magnetic fields gets stopped at our skin?
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2answers
61 views
Special Theory of relativity on electromagnetic waves
Since time slows down and length contracts, when we travel almost at speed of light, if the speed of light (or EM waves) remains same and the wavelength of light remains same, do we measure the ...
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2answers
168 views
Counting electromagnetic modes in a rectangular cavity and boundary conditions
The electric field in a cubical cavity of side length $L$ with perfectly conducting walls is
$E_x = E_1 \cos(n_1 x \pi/L) \sin(n_2 y \pi/L) \sin(n_3 z \pi/L) \sin(\omega t)$
$E_y = E_2 \sin(n_1 x ...
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2answers
201 views
Microwave absorption in tissue
Why do I have a big microwave absorption in tissue, when the tissue conductivity is high? I thougt the opposite would be correct. Can somebody explain the reason?
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1answer
180 views
How did Lord Rayleigh derive/determine the phase function for his scattering model?
I've been researching the question for quite some time, as I understand it the phase function is actually an approximation due to the particle-wave duality inherent in participating media such as the ...
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1answer
45 views
Is the de Broglie wavelength of a photon equal to the EM wavelength of the radiation?
Is the de Broglie (matter) wavelength $\lambda=\frac{h}{p}$ of a photon equal to the electromagnetic wavelength of the radiation?
I guess yes, but how come that photons have both a matter wave and an ...
1
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1answer
158 views
Two photons transition
if an atom in its ground state is coupled to an electromagnetic field it can absorb a photon if the EM field contains one with the right frequency. These transitions depends on $⟨f|H_i|i⟩$ (from ...
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1answer
226 views
Optical constants of noble metals: the Drude model for microwave modelling
I have a question regarding the optical constants of noble metals.
According to Johnson and Christy's paper Optical Constants of Noble Metals (Phys. Rev. B 6, 4370–4379 (1972), ...
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1answer
58 views
Could we really charge metal plates using microwaves?
While skimming through Dielectric heating, I read that they use microwaves to charge the plates. How do they do that?
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1answer
46 views
Where is the amplitude of electromagnetic waves in the equation of energy of e/m waves?
Does the amplitude of the photon oscillations always stay constant and if it is not - what are the physical differences between the photon with higher amplitude in comparison to the one with the less ...
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1answer
49 views
Fundamentals of electrostatics
Suppose I have a Gold Leaf Electroscope and the leaves are observed to diverge by a certain amount. Now if I send a beam of X-rays and allow it to fall upon the electroscope for a very short period of ...
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1answer
45 views
Electromagnetic field to cool a substance?
I saw somewhere that an electromagnetic field would cause a substance to let off thermal energy, ultimately resulting in the substance to cool really quickly.
If this is possible, does the strength ...
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1answer
380 views
Oscillating Dipole: Principle of Receiving and Transmitting Electromagnetic wave?
I am practising to Tfy-0.1064 -elementary-physics-exam and doing this practise -exam here. The problem in Finnish goes like this:
"Selosta lyhyesti sähkömagneettisen säteilyn lähettämisen ja ...
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0answers
233 views
Do EM waves transmit spin polarization?
Suppose you have a normal dipole antennae (transmitter and receiver) . Spin polarized current (as opposed to normal current) is sent into the transmitter, it emits an EM wave and the Receiver receives ...
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47 views
How strong must a signal be at the edge of the Solar System to penetrate into the Sytem?
A sort-of follow-up to Are the Voyager probes still sending us a signal ?
Still following on the news report referenced in the above question, this report indicates further magnetic surprises at, or ...
2
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0answers
13 views
Radio antennas that are much shorter than the wavelength
From my limited experience with ham radio when I was a kid, I expect transmitting and receiving antennas to have lengths that are on the same order of magnitude as the wavelength, and in fact I recall ...
2
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0answers
40 views
Mathematical equivalence between Liénard-Wiechert potential and 4-potential in Rindler coordinates
I'm studying the problem of the radiation of an uniformly accelerated point charge:
$$x^{\mu}(\lambda)\to(g^{-1}\sinh g\lambda,0,0,g^{-1}\cosh g\lambda)$$
I found that when a point charge is moving ...
2
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0answers
38 views
Analytical solution of two level system driving by a sinusoidal potential beyond rotating wave approximation
A quantum mechanical two-level system driving by a constant sinusoidal external potential is very useful in varies areas of physics. Although the wildly used rotating-wave approximation(RWA) is very ...
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0answers
137 views
Classical blackbody radiation 'solution'
I never understood how the equipartition theorem was applied electromagnetic waves inside the metallic blackbody. As hyperphysics puts it ...
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0answers
86 views
Macroscopic chromodynamics
Lately I've been reading about gamma ray lasing phenomena, and I've been wondering about the applications of this.
More concretely, the above fantastic question led me to wonder if we could somehow ...
2
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0answers
115 views
What is the attenuation spectrum of radio waves in pure water?
Here is a plot of microwave attenuation in atmosphere:
(source)
I'm looking for a similar plot, but for pure water, and a frequency range covering at least 100 MHz to 2 GHz, hopefully more.
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0answers
185 views
Cerenkov light - a practical calculation
I need to calculate the approximate total amount of energy radiated, via Cerenkov, by a muon as it traverses $10\:\rm{cm}$ of quartz glass. Unfortunately I've spent so much time fiddling with ...
2
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0answers
118 views
Modeling a spray painted polyurethane surface reflection
I'm modeling light interaction/reflection from a fiberglass surface with polyurethane epoxy (that is very reflective) that has been spray painted with a matte black paint. I'm looking for some input ...
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0answers
43 views
Longitudinal EMAG wave?
I'm reading about optical waveguide analysis, and often come across the terms "transverse electric mode" vs. "transverse magnetic mode". As I unerstand, it means that the electric/magnetic field has ...
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0answers
46 views
Fourier Transform of ribbon's beam Electric Field
I have a monochromatic ribbon beam with $E(x)e^{i(kz-\omega t)}$ being the electric field's amplitude. I want to show that the lowest order approximation in terms of plane waves is
...
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0answers
132 views
Is there any example where electric and magnetic fields are not perpendicular?
Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
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0answers
23 views
Does shadow fading change if obstacles are fixed?
Given a RF sender and a receiver, suppose the obstacles between them are fixed, both their material and dielectric properties, does the path loss caused by their shadowing vary? If yes, what causes ...
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0answers
21 views
Phase functions non-existent in original (J. Strutt) Lord Rayleigh's work?
This is related to my previous Phys.SE question on the derivation of the phase function - upon sifting and scanning through 600 pages of John Strutt's collected work, there is absolutely no mention of ...
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0answers
76 views
How to calculate radiative transition rate of exciton in a quantum dot with specific dimension?
I am writing rate equations for a nanophotonic system including three quantum dots. I need to calculate that radiative transition rates of exciton in ground state in those quantum dots.
In the paper ...
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0answers
242 views
What happens with photon when it is slowed down substantially?
In a dispersive media light's velocity can change substantially. Imagine we can slow it down to near 0 what the wave would look like?
Frequency of light does not seem to change even at v=0 (at least ...
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0answers
244 views
Equations governing mutual inductance and transformers
What are equations for voltage ratio (primary/secondary) of...
the action of a transformer with a turn ratio (turns primary/turns secondary) of X/Y and a toroidal core of cross-sectional radius R ...
1
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0answers
43 views
References for Radio Optics?
I'm really intrigued by a bunch of questions like 'what do radio waves look like?' 'how much RF radiation is there in the town I live in?' 'why does RF imaging work?'
But I think I need to do some ...
1
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0answers
98 views
What narrow-linewidth laser system runs at 2100nm with 1W of power?
For an experiment at our university we need a laser that runs at about 2.1 μm (about 20nm higher or lower would be fine too.
We have found a multitude of lasers that achieve this (typically Thulium- ...
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0answers
50 views
EM Field having simultaneously minimum divergence and minimal transversal extension
I read that the field that have simultaneously minimum divergence and minimal transversal extension is the fundamental Gaussian mode. What are the good references in this subject, to prove the ...
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0answers
16 views
Object $A$ : Object $B$
Object $A$ has the ability to send information via some wavelength.
Object $B$ houses object $A$ and has the ability to detect when wavelengths are transmitted.
What is object $B$?
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0answers
55 views
Curie's principle in electromagnetic field theory
I am looking for some explanation and if possible also some references about the applications of Curie's principle in electromagnetic field Theory, precisely in the computation of magnetic (resp. ...
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0answers
36 views
Time reversed laser
Recently, I read an article on time reversed laser. I don't know why they call it a time reversed. I have a doubt that why they use two laser in the device. And what is an anti-laser?
The device ...
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0answers
41 views
EigenMode expansion for beam propagation
I want to understand how to apply EigenMode expansion method (http://www.photond.com/files/docs/PW03_eme_paper.pdf) for beam propagation on a system of lenses.
The interface between two mediums of ...
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0answers
44 views
Should a 1D Guassian wave oscillate?
I wrote a few lines that numerically solve Maxwell's equations.
The result is a moving wave that looks like a single pulse.
This looks strange to me because I expect waves to move in oscillator ...
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0answers
71 views
Absorbance by using Poynting vector
How should I compute the amount of energy of an EM wave absorbed in the material?
Can I just use the divergence times the Poynting vector?
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0answers
207 views
What is the correct definition of “group velocity dispersion”?
When we talk about a medium with dispersion, we can define the phase velocity $v_\phi = \omega/k$ and the group velocity $v_g = d\omega/dk$. Likewise the phase index $n = c/v_\phi$ and the group index ...
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0answers
53 views
Currents and fields of a magnetron
I can't make heads or tails of the descriptions of magnetrons (i.e. microwave) I'm reading online. Hyperphysics does the best job of illustrating fields and currents, but the story of its operation ...
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0answers
57 views
Formula for transverse decrease in signal strength?
Alice is transmitting an electromagnetic beam to Bob.
Assume it is a well collimated beam, like a laser beam, or a maser beam.
As Bob's distance from Alice increases, his signal strength decreases ...
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0answers
84 views
Wireless signal strength
My question is possibly somewhat misplaced, but I'll try to explain as best as I can. Suppose I have a transmitter with a frequency of 2500MHz and a power of 1W. It radiates uniformly in all ...
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0answers
128 views
Transmission formula for two near field polarizing filters?
Consider two parallel wire "comb" filters oriented at 45 degrees relative "tooth" angle.
The comb tooth spacing spacing is much less than one wavelength, and the comb tooth length is much more than ...
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0answers
154 views
Lorentz transformations of the polarization vector
Let $\bf{n}'$ be a unit vector in the direction of a wavevector in the plasma rest frame and $\bf{B'}$ be a unit vector along the magnetic
field in the plasma rest frame. The electric field of a ...
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0answers
59 views
MIT's 230% efficient LEDs. A reprise about cooling
This is a reprise of the question Can someone explain the science behind MIT's 230% efficient LEDs?
The PRL paper doesn't detail what the efficiency of heat-to-light energy conversion is, which in ...
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0answers
187 views
Is Photosynthetic Photon Flux Density (PPFD) a synonym for Photosynthetically Active Radiation (PAR)?
Both have units of $\mu\text{mol m}^{-2}\text{s}^{-1}$ and refer to light in the 400-700 nm range - that activates photosynthesis. However, I just want to confirm that these are synonyms and don't ...
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0answers
112 views
What is the electric field part of an EM wave? Radiation field or the induction field?
Look at this image:
I wonder if the electric field is from the induction field from a vibrating electron or the radiation field? If it is from the radiation field, as I suppose, than can someone ...
