Questions tagged [electromagnetic-radiation]
Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.
5,641
questions
0
votes
0
answers
26
views
Is there a substance which can pass both IR and UV radiations?
I have been thinking about this for a while. A quartz prism allows UV Radiation to pass. A rock salt prism allows IR radiation to pass. Glass absorbs both.
Is there something, that is, a substance to ...
-3
votes
0
answers
20
views
Is there an IR-camera-detectible color that can be the coat for a material to transfer the material heat by emitting into the space? [closed]
If we see a material it is coloured in a color that our brain could easly recognize. But when we look at it by the help of an IR camera it could also be coloured and if two materials have same ...
0
votes
0
answers
14
views
How to use dipoles to enforce the boundary conditions for a spherical dielectric with complex permittivity
I want to impose an electric and magnetic field on a spherical dielectric of radius $ R $ and relative permittivity $\epsilon_r=\epsilon'+i\epsilon''$. Say the fields are slowly-varying (like a plane ...
- 1
-1
votes
0
answers
34
views
Stefan-Boltzmann's law independence of surface density
One thing about Stefan-Boltzmann's law didn't make sense to me is that the radiated power density is independent of the particle density of a surface. It seems like things have to cancel out amazingly ...
2
votes
0
answers
31
views
Link between photon helicity and polarization of $A^\mu$ electromagnetic potential
From Wigner theorem we know that the irreducible unitary representation of the Poincarè group for massless and spin 1 particle is labelled by the momentum $p_\mu$ and the two possible helicity $+1,-1$ ...
- 613
1
vote
0
answers
39
views
Does electric and magnetic field from electromagnetic radiation are 2D based? [closed]
I'm getting into physics, specially in electromagnetism.
When we're talking about electromagnetic radiation. Does it has a 2D shape when it's propagating through space?
Does Maxwell's equations ...
- 11
-4
votes
2
answers
82
views
Can we catch signals from a cellphone using an external device? [closed]
What if someone stole em waves from our mobile devices to listen to our conversations or get our OTP. Whatever encryptions they have they are just EM waves innit and they cannot be propagated only in ...
0
votes
0
answers
43
views
How well does a cavity with a hole approximate a black body?
Cavity with a hole is a frequently cited approximation to a black body (more precisely, it is the hole that is the black body here):
Is there a simple estimate of how well such a cavity approximates ...
- 60.3k
0
votes
2
answers
123
views
Diffraction when the wavefront is not parallel to the plane
I am studying Feynman's chapter on the origin of the index of the refractive index (see this link).
If I am not mistaken, what he does is to prove that when a wave enters a medium (modelled as a ...
- 507
1
vote
0
answers
42
views
Dipole antennas and the $B$ field
A dipole antenna responds to the electric component of a EM wave. Does the magnetic component of a EM wave have any effect on the performance of a receiving dipole antenna?
- 55
1
vote
0
answers
17
views
Will an electron release energy when it is added into an atom for which electron affinity value is negative (endothermic)?
According to my understanding, when an electron is added into an atom, it emits energy in the form of photons because it is a form of de-excitation or relaxation. This is when electron affinity will ...
- 11
6
votes
7
answers
3k
views
How does light beyond the visible spectrum relate to color theory?
Like if you put a red spotlight and a blue spotlight on the same area, the light ends up magenta. And if your light is purple and you have a yellow chair, the chair will appear black because the ...
0
votes
1
answer
67
views
Why is the length of a Faraday cage's lattice relevant to what wavelengths it blocks?
I believe the title is self-explanatory. I see a similar reasoning pop up often in other areas where EM radiation is being manipulated, e.g. lasers, radars, radio telescopes and so on.
The wavelength ...
- 132
1
vote
0
answers
27
views
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 ...
- 692
1
vote
0
answers
41
views
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 ...
- 692
15
votes
7
answers
2k
views
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 ...
- 161
2
votes
0
answers
38
views
Direction of propagation of extraordinary wave inside a 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 ...
- 21
0
votes
1
answer
49
views
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 ...
- 273
0
votes
0
answers
26
views
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 ...
- 1,538
3
votes
3
answers
182
views
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 $2M$ ...
- 1,161
1
vote
1
answer
46
views
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 ...
0
votes
0
answers
96
views
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_{...
- 123
1
vote
1
answer
52
views
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 ...
6
votes
2
answers
586
views
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-...
- 63
1
vote
1
answer
40
views
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 ...
- 437
4
votes
1
answer
103
views
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 ...
11
votes
4
answers
2k
views
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?
- 959
2
votes
0
answers
25
views
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 ...
- 165
0
votes
1
answer
100
views
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 ...
- 185
0
votes
4
answers
129
views
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....
- 1