New answers tagged electromagnetic-radiation
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Spontaneous emission as dissipation and fluctuation
After randomly wandering around for quite a while I found the answer. Yes, energy accumulated in the material because of light absorption does go out as spontaneous emission, and yes, the effective ...
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Does polarization of linearly polarized radiowave change on reflection
It's a little confusing when you say "surfaces"..does that mean a single bounce considered over different surfaces (flat, or not), or a multi-bound single return from a so-called scene?
The ...
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Does polarization of linearly polarized radiowave change on reflection
Generally speaking yes. Specifically, the so-called s- and p-polarizations reflect with different phases that depend on parameters such as refractive indices on the media and the angle of incidence/...
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The 3.7 m dish antenna of Voyager
From Wikipedia: "16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (Sun sensor/Canopus Star Tracker) to maintain pointing of the high-gain antenna ...
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Derivation of the Classical Lifetime of Hydrogen
Some derivations (such as this one: Classical Lifetime of a Bohr Atom ) do not assume circular orbits, but instead they consider nearly circular orbits as suggested towards the end of the original ...
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Derivation of the Classical Lifetime of Hydrogen
For precise number one would indeed need to do what you described - take into account that radiation rate depends on the radius of the orbit which is changing in time.
But the logic of the QM fathers ...
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Vector Potential and Electric Field
Yu uses cgs units. In cgs units, the electric field is
$$\vec{E} = -\frac{1}{c}\frac{\partial \vec{A}}{\partial t}\ , $$ (see eqn. 6.24 in Yu)
and $c =\omega/q$.
If $E = E_0 \sin(\vec{q}\cdot \vec{r} -...
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Vector Potential and Electric Field
In page 260 the conjugate term is explained: it's used so that $A$ is a real function. Remember that $e^{ix}+e^{-ix}=2\cos x$. As for the constant terms that appear in the equation for $A$, I think it ...
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Is the spectrum of Hawking radiation identical to that of thermal radiation?
There are a few instances where EM loses to other thermal radiation:
Core collapse supernova (100 GK): 99% of the BB radiation is neutrinos. When you have $10^{57}$ nucleons in the volume of the size ...
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Is the spectrum of Hawking radiation identical to that of thermal radiation?
Roughly speaking, a system is said to be thermal if the probability density of a particle at energy $E$ is $p(E) = {\cal N} e^{-E/T}$ (in natural units), where ${\cal N}$ is some constant that we fix ...
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Is the spectrum of Hawking radiation identical to that of thermal radiation?
In everyday life thermal radiation means electromagnetic radiation simply because in everyday life thermal energies are too low to produce massive particles. The lightest massive particle (apart from ...
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Linear-array diffraction beam splitter
Figured it out. The GDCalc example uses a Gaussian beam as the incident field. In order to see the correct number of diffracted beams, the waist of the Gaussian beam needs to be increased from the ...
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Turning monochromatic light into polychromatic light using shutter?
It would be hard to do the experiment you describe using any form of mechanical shutter as the duration of the pulse has to be very short to significantly increase the bandwidth of the light. You'd ...
- 359k
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Coaxial cable and faraday cage: why those shielding properties precisely?
But is it still true in the context of wave propagation?
Yes, a coaxial cable still has its shielding effect during wave propagation.
If I assume I send a current pulse on the outer shield, will it ...
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If light is electromagnetic then can light produce electricity or attract metals?
“if light falls on a metal it should produce current due to its electric nature but it doesn't” What make you think “it doesn’t “‽
“ due to its magnetic nature shouldn't it attract metal object” Not ...
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Polarization rotation: Jones Matrix that maps Horizontal to right circular
I know this is an old question, but anyways -
physically, that would correspond to sending a beam of polarized light through a halfwave plate followed by a quarterwave plate; for initial beam states ...
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Do gravitational waves cause matter to radiate?
It depends on your exact setup but in theory you could arrange for gravitational waves to generate electromagnetic radiation, however in practice I don't think this scenario is very plausible to occur ...
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Do gravitational waves cause matter to radiate?
Let us assume that our gravitational waves are described by a linearized Einstein equation, so that the metric is of the form
$$
g_{\mu\nu} = \eta_{\mu\nu} + h_{\mu\nu}
$$
Where $\eta_{\mu\nu}$ is the ...
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Time reverse of circular polarization
I think you are right to conclude that the circular polarisation would not be reversed by time reversal. One conventional and consistent way of defining circular polarisation is the right hand rule. ...
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Time reverse of circular polarization
We use a photon instead of a plane wave. It has a momentum $\vec p=\hbar \vec k$, a spin $\vec\sigma$, and a helicity:
$$ h = \vec{\sigma}\cdot\vec p$$
and it is helicity, not spin, that we associate ...
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