Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.

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91 views

Why is it that fractal antennas can filter out so many frequencies?

As known, fractal antennas are used for example in cell phones. But why is it that so many different kinds of frequencies can be filtered out of the forest of radio waves surrounding us? Is it because ...
7
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123 views

Experimentally diminishing random errors for low wavelength UV observations

Part of the work that I do involves observations of solar low wavelength UV observations, specifically UV-B and UV-A II (up to 340nm). I have noticed that when I observe responses on a CCD or CMOS ...
5
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308 views

Mirrors and light beam divergence technology limits

There are many applications for orbital space mirrors in astronomy (better telescopes) and space propulsion (solar power for deep space probes), but this is limited by the minimum beam divergence ...
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57 views

Seeing light source from its diffracted light

Even if the line of sight is blocked by something(like a wall as in figure) will I able to see the light source if I see the diffracted light of the source? 1.Will the observer no. 2 see the light ...
4
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140 views

The logarithmic decay of WIFI

I have been told that Wi-Fi, LTE etc signal strength fall of as $$\propto \frac1{\log(r)}$$ where $r$ is the distance. I am wondering why this is. I better explain what I mean with this question. ...
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21 views

Determination of temperature from electromagnetic emissions

The actual measured radiation intensity at different frequencies varies significantly from the ideal theoretical Planck curve. For example, here is the result of a typical laboratory measurement at ...
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48 views

Will the photon wavelength fluctuate in the presence of a gravitational wave?

The microwave background is due to the expansion of the Universe where the wavelengths of radiations are stretched by spacetime. As in the LIGO experiment, in the presence of gravitational wave, ...
3
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0answers
81 views

Why must this boundary condition be met? (Electromagnetic wave at interface between two mediums)

My textbook says that The laws of Electromagnetic Theory (Section 3.1) lead to certain requirements that must be met by the fields, and they are referred to as the boundary conditions. ...
3
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70 views

Estimating temperature with Boltzmann relation with split emission lines

I'm trying to estimate the temperature of a plasma through the use of hydrogen lines, $H_{\alpha}$ and $H_{\beta}$ using the Boltzmann relation: $$ \frac{ n_{2} }{ n_{1} } = \frac{ g_{2} }{ g_{1} }e^...
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46 views

Why is the susceptibility $\chi(t)$ real?

So my question is quite simple I suppose, and perhaps trivial. It is known that the frequency domain susceptbility $\chi(\omega)$ is complex, and that the two parts can be related with the Kramers-...
3
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141 views

Dispersion of light in metals and the plasma frequency

I've been reading about the dielectric function and plasma oscillations recently and I encountered the following dispersion relation for EM waves in metals or in plasma (Is it correct to treat those ...
3
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124 views

Clarification about Bragg's law explanation

The Wikipedia has this illustration of Bragg's law and then says The two separate waves will arrive at a point with the same phase, and hence undergo constructive interference, if and only if ...
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212 views

Free charge movement in an electric field - including bremsstrahlung

Let us imagine a free, negatively charged object that is in rest and placed in an elecric field of a point positive charge. The positive charge has a huge mass and cannot move, so we consider only the ...
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928 views

Questions about Michelson interferometer

I have been doing experiment on Michelson experiment, but I don't quite understand why white light results in an interferogram with very few fringes, and why are they necessarily Gaussian? I know that ...
3
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682 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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39 views

Plasmon quenching vs plasmon decay. What is the difference?

I'm reading an article "Quenching, Plasmonic, and Radiative Decays in Nanogap Emitting Devices" (pubs.acs.org/journal/apchd5). I don't understand the following: Counterintuitively, we evidence ...
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47 views

Have gravitational waves any effect on the electromagnetic waves in interferometers?

I am not into general relativity, but the explanation of how an interferometric gravitational antenna works is generally pretty basic. In the recently published paper announcing the detection of ...
2
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56 views

Electric field due to a current carrying loop

I want to know how I can calculate the radiated electric field in the far zone of the loop. Knowing that the loop is in center at the origin of a x-y plane Knowing that the loop as a time-harmonic ...
2
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29 views

How to mathematically model a realistic aperture illumination?

I want to know a mathematical expression that I can use to model a realistic aperture illumination to produce the primary beam of an antenna so that the radial distribution of this aperture ...
2
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0answers
97 views

Higher order multipolar second harmonic generation in centrosymmetric materials

As is pointed in this question, second harmonic generation is forbidden in the bulk of the materials possessing centrosymmetry. In some papers it is said that in the dipolar approximation the SHG ...
2
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113 views

Phased non linear array antenna - First Sidelobe

I have a problem I cannot seem to solve and I REALLY need some help. It's about phased-array antennas whose dipoles are not equally spaced, not equally phased, not equally fed (amplitude). Let's ...
2
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343 views

Proof that electric and magnetic fields in a EM wave are perpendicular

Is there a general proof, that for electromagnetic waves the magnetic and electric fields are perpendicular? The only ones I can find only focus on plane waves.
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46 views

X-rays scattered at righ angles of the incident ones: are they polarised?

Basic books dealing with the interaction of X-rays with matter ussually don't mention anything about the polarisation, but I read somewhere that X-rays scattered in matter are linearly polarized, ...
2
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40 views

Where does the factor of $\gamma^2$ come from in synchrotron radiation?

I've read the derivation for synchrotron radiation (as derived by Griffiths), so I know how to get it given the retarded potentials, etc. I'm having a hard time with intuition. The derivation in ...
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180 views

What is the relation of scattering, extinction and absorption cross sctions with scattering parameters?

In optics and electromagnetics, they frequently calculate the extinction, scattering or absorption cross sections of a single particle (e.g. a sphere). Scattering cross section which is the ratio of ...
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22 views

Main differences between elastodynamic and light scattering when using S-matrix to find bound states

What are the main differences (top 5 if question is too broad), for using the S-matrix to find bound states, between elastodynamic and light scattering? (if it facilitates a higher quality question/...
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125 views

What is the highest frequency directly detected?

The Feynman Lectures of Physics states: In fact, although we mentioned many frequencies, no phenomenon directly involving a frequency has yet been detected above approximately $10^{12}$ cycles per ...
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25 views

Where does 1/Gamma characteristic angle come from in EM Radiation?

Very curious as to where this angle comes from? It describes the peak of radiation for almost all radiation regimes, but I am having a difficult time seeing where it comes from. Also, the physical ...
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994 views

The physical meaning of electromagnetic wave

What, fundamentally, is an electromagnetic wave? As far as I know, all wave phenomena are derivations of an oscillating processes, e.g. particles vibrating in a medium. I can't imagine a wave process ...
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95 views

Mie Scattering for spheres with constant dipole moment

I was wondering whether there exists a theory that describes Mie Scattering for spheres that have a constant dipole moment. Since there are theories that describe Mie scattering in the case of a ...
2
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0answers
194 views

Charge above a conductor; effects due to Lorentz force law for moving charges

Currently working through a practice preliminary examination problem. I have your standard charge situated a distance d from a infinite conductor(lets say in the $\hat{z}$ direction and neglecting ...
2
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0answers
388 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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232 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 $\mathbf{E}(x,z,t)=...
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327 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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295 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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944 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 ...
2
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94 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
422 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
168 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
38 views

Is it possible in this Universe to communicate a bit of information with energy that scales sub-linearly with distance?

If we look at all the ways that people do communicate information, they all seem to have a cost "at least linear in distance." For example, communicating over a wire has attenutation, so the energy ...
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66 views

Time involved in reflection

Consider light bouncing back and forth between two ideal front surfaced mirrors. How long does the process of reflection (i.e., absorption and re-emission) take?
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56 views

Why is 2000 grit good enough for a mirror finish?

The mean particles size on a 2000 grit sandpaper is ~ 1 um, which is not that smooth compared with the wavelength of visible light. But usually when I want a mirror finish, 2000 grit will provide a ...
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0answers
59 views

advantages/disadvantages of a cylindrical microwave oven cavity in comparison to a rectangular cavity

Why are rectangular cavities preferred for standard microwave ovens with a frequency of 2.45 Ghz? What is the reason that you can hardly find a circular cavity? What are the disadvantages of ...
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0answers
16 views

What wavelengths of electromagnetic radiation are emitted by the LH2/LOX reaction?

Rocket engines such as the Rocketdyne Rocket System 68 and the Space Shuttle Main Engine use liquid hydrogen and liquid oxygen as propellants. The exhaust from this type of engine is notable in ...
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94 views

How to derive equation for time it takes photons to diffuse through the Sun

I am wanting to use the Rosseland radiative heat flux equation to find the time it takes for photons to diffuse through the sun. The answer I am wanting to derive is: $$\tau_D~\frac{\rho \bar C_p R^...
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0answers
44 views

Can 2 photons make up the same colour as another photon?

So, my question deals with the excited electron shown above. (1st diagram) This electron can return to its ground state by either of two ways. One of the ways involves the emission of 2 photons. (2nd ...
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0answers
23 views

Dependence of Noise Tolerance of waves

Electromagnetic waves are used for transmission of any message. And different kinds of waves have different noise-tolerance. If my guess is right then the noise tolerance is a property of wave which ...
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0answers
13 views

What dictates the range of EM radiation which can be produced by semi-conductor excitation (like LEDs)

Exciting semiconductors such as silicon carbide and gallium nitride can cause electroluminescence. I believe that by altering the chemistry of the semiconductor, you can alter the wavelength of the ...
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25 views

Is frictional heat just electromagnetic interactions creating infrared radiation?

Example: Rub your index finger on a sheet of paper and you will feel that it will get noticeably hotter Is the reason you feel this increase in heat (technically an increase in kinetic energy of the ...
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69 views

Do all particles have radiative transitions?

Everybody knows that excited electrons can emit photons upon relaxation. A nucleus too (which is not an elementary particle), can be in an excited state and emit gamma rays upon relaxation: (source) ...