Questions tagged [electromagnetic-radiation]
Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.
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What actually happens when light goes into a waveguide?
I have only dealt with a rudimentary theoretical treatment of how light propagates inside a waveguide, such as those available in Griffiths.
One thing bugging me is that I still do not know how ...
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About the notation for TEM waves
I just came across this article where the term "$\mathrm{TE}_{101}$ microwave mode" is mentioned. Other than the basics of TEM waves which I learned in Griffiths, this is the first time I ...
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Why does the length of an antenna matter when electromagnetic waves propagate perpendicular to the antenna?
The optimum length for a dipole antenna is a multiple of half the wavelength that it is designed to receive or emit. Why is this? If an electromagnetic wave has E in the x-axis, B in the y-axis, and ...
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Double refraction - Direction of propagation of extraordinary wave inside the birefringent medium
I am reading Optics by Ajoy Ghatak, in which the author explains the phenomenon of double refraction in a calcite crystal using Huygens' principle. My query is in the analysis of the case of normal ...
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What is the electric field strength of a photon? In $\rm V/m$ or $\rm N/C$? Or its magnetic field in Gauss or Tesla? For visible light, or gamma rays? [closed]
I am thinking of this now because I have been learning about the Schwinger limit (or Schwinger effect)...
Supposedly, a strong-enough electric and/or magnetic field creates a 'nonlinear' effect in the ...
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Why does radiation of small wavelength interact with small objects?
I was reading chapter 2 from the book 'Diagnostic Radiology Physics : A handbook for Students and Teachers', and came across the following quote
"X rays of energy of a few tens of ...
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Solarization Spectrum
I'm looking to better understand the relation between the spectrum of the light which induces solarization in glass and the spectrum of the induced absorption.
More specifically, I'm interested in ...
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Photonic black holes
"Can a photon turn into a black hole?" - usually the answer to this question is - it can't, because it has zero rest mass. However, when we derive the Schwarzchild Metric initially the $2M$ ...
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Is it possible for both electric and magnetic fields to have longitudinal component in a rectangular waveguide?
I know a rectangular waveguide cannot support TEM waves, but supports TE and TM waves. In the TE mode, $E_z=0$ and in the TM mode, $H_z=0$ (where propagation direction is along the $z$-axis). I want ...
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How to compute the diffraction efficiency of a thin phase grating with arbitrary groove shape?
From Magnusson and Gaylord (1978), the wave amplitudes, $S_i(z)$, of $p$-polarized light for a thin, arbitrary phase grating are given by the equation
$$
\frac{\partial S_i}{\partial z} + \gamma \sum_{...
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Confusion regarding phase
As far as I know about phase if the phase difference between two waves is positive, the former is leading..and the latter is lagging. Then why has D J Grifith stated this?
If the phase of the magnetic ...
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Could a transparent frequency-altering material be possible?
I would imagine a material that is transparent but a electromagnetic wave going out will have a lower frequency than when going in (and maintaining it's direction). You could build glasses to see UV-...
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Can an optical medium be lossless and dispersive?
Occasionally, I come across the phrase "lossless dispersive linear optical medium". How can such a medium be possible mathematically? I mean the real and imaginary parts of the electric ...
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About electron radiation frequency in Heisenberg's 1925 paper
In Heisenberg's 1925 article Quantum Theoretical Interpretation of Kinematic and Mechanical Relations, one of the first things he establishes are the form of the frequency functions in (what I assume ...
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Can the laser light, in principle, take any wavelength in the EM spectrum?
Can the laser light, in principle, take any wavelength in the EM spectrum? I don't think there is what prevent this in principle, right?
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ELF Electromagnetic wave propagation in plasma (ionosphere) - how?
Can an extremely low-frequency electromagnetic wave (below 500 Hz for example) propagate through an ionosphere? The cutoff frequency of Earth-ionosphere waveguide is approximately 1.7 kHz so I ...
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How many photons pass through us every second?
I just read this answer https://physics.stackexchange.com/a/229374, which says that, when a magnet rotates, photons are emitted with wavelength $λ=c/f$, where $f$ is the frequency of rotation. And ...
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Why should an electron falling into the nucleus, according to the Maxwell's laws of electrodynamics, destroy the atom?
It is often said in physics and chemistry classes and textbooks that atoms must be unstable when the electron continuously loses energy and finally fall into the nucleus according to classical physics....
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Does the Larmor Formula assume circular motion?
The Wikipedia page on the Larmor formula says that
the Larmor formula makes the unavoidable assumption that the charged particle is orbiting in a circle.
This quoted sentence isn't true, correct? I ...
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How can photons interact with nuclei?
How can photons such as X-rays or gamma rays interact with the nuclei of atoms given that, as I understand it, the length scale of a nucleus is around a couple of femtometers? So, shouldn’t the size ...
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Is luminescence from impact of fast neutral atoms/molecules on a suitable substance known?
Cathodoluminescence is emission of photons by electrons impacting on a luminescent material.
The Rutherford scattering experiments detected impacting helium nuclei on a phosphor screen.
Many other ...
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Why does oxygen green (S1) emission in aurorae only occur at lower altitudes? [duplicate]
Aurorae have a red color at high altitudes caused by the excitation of atomic oxygen and the subsequent emission at about $630 \,\text{nm}$. This happens at high altitudes because at that height there ...
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Can gravity radiate?
In electromagnetism, when a charge accelerates, it emits radiation. We know this because we can write the retarded potentials, apply $\vec E=- \nabla V-\frac{\partial \vec{A}}{\partial t}$ and $\vec B=...
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What do we mean when we say the CMB has a temperature and how do we measure it?
I have read this:
An object without any internal degrees of freedom, like a single photon, can't really have a temperature. But an ensemble of photons can have a temperature. If you put an ensemble ...
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dipole-radiation in semiclassical dynamics solid state
Using the semiclassical dynamics in solid state physics (electrons on a lattice with periodic potential, constrained to a band structure), we usually obtain that in the presence of external fields (...
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Why is the Poynting flux not conserved across the interface between two conducting materials?
This question is part of my attempt to use an answer to another question I've posted on this site.
If I have two materials with complex indices of refraction, $\widetilde{n}_0$ and $\widetilde{n}_1$, ...
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Confusion about EM spectrum and the Fourier transform
Since courses on signal analysis and electromagnetism I have become confused about what the spectrum of electromagnetic radiation really means. I know light is when electric and magnetic fields become ...
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Dipole radiation of a non-relativistic electron in elliptic motion [closed]
I'm trying to solve the following problem:
A non-relativistic electron is moving in elliptical motion inside a positively charged cylinder of homogenous charge density $\rho$. The initial radius ...
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