All Questions
Tagged with electromagnetic-radiation energy
31
questions
38
votes
4
answers
5k
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Redshifting of Light and the expansion of the universe
So I have learned in class that light can get red-shifted as it travels through space. As I understand it, space itself expands and stretches out the wavelength of the light. This results in the light ...
- 3,871
49
votes
8
answers
23k
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Amplitude of an electromagnetic wave containing a single photon
Given a light pulse in vacuum containing a single photon with an energy $E=h\nu$, what is the peak value of the electric / magnetic field?
- 1,056
12
votes
3
answers
6k
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Explain how (or if) a box full of photons would weigh more due to massless photons
I understand that mass-energy equivalence is often misinterpreted as saying that mass can be converted into energy and vice versa. The reality is that energy is always manifested as mass in some form,...
- 21.1k
54
votes
5
answers
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Are there any theoretical limits on the energy of a photon?
Is there any lower or upper limit on the energy of a photon? i.e. does the mathematical framework we currently use to study photons blow up when a photon surpasses a certain upper limit of energy? (or ...
- 7,319
6
votes
3
answers
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Is the energy of a photon continuous/discrete?
I was struggling today with this question: does a free photon have a continuous energy spectra?
Free means in no context of any energy system (eg. an atom, em field). Although I'm asking myself if ...
- 63
6
votes
2
answers
14k
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The energy of an electromagnetic wave
The intensity of an electromagnetic wave is only related to its amplitude $E^2$ and not its frequency. A photon has the same wavelength as the wave that's carrying it, and its energy is $h f$.
So ...
- 309
8
votes
3
answers
2k
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How much light is there in space and how heavy is it?
Our night sky is filled with stars. On a dark night a significant fraction of the sky is light. This light, we are told, has been in transit for many millions of years. There must therefore be quite a ...
- 219
25
votes
3
answers
8k
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If energy is quantized, does that mean that there is a largest-possible wavelength?
Given Planck's energy-frequency relation $E=hf$, since energy is quantized, presumably there exists some quantum of energy that is the smallest possible. Is there truly such a universally-minimum ...
- 453
10
votes
4
answers
3k
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Standard formula for energy density of electromagnetic field
The formula for energy density of electromagnetic field in electrodynamics is
$$\frac{1}{8\pi} (\vec E\cdot\vec D+\vec B\cdot\vec H).$$
This formula appears in all general physics courses I looked at. ...
- 2,226
4
votes
1
answer
1k
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Refraction: Energy flow, tunneling and Evanescent EM waves
In the full internal reflection case where we have a refracted evanescent wave, If another object is nearby, then we could have wave tunneling phenomenon(frustrated total internal reflection). I am ...
- 7,720
2
votes
2
answers
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The Quantization of Photon Energies [duplicate]
Despite Planck's constant being in $E=hf$, it would appear to me that energy is still not discrete, as frequency can be an fraction of a Hertz that one wants. How does this imply that electromagnetic ...
user24082
1
vote
1
answer
423
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Energy carried by Electromagnetic Waves
The energy density carried by monochromatic planar Electromagnetic Waves is defined as:
$ u = \epsilon_0 E_0^2 cos^2(kz-\omega t + \delta)$
As this wave travels, it carries this energy along with it.
...
- 453
-4
votes
2
answers
4k
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Do all the photons have the same energy? [duplicate]
The title is pretty self-explanatory. Do all the photons have the same energy?
- 89
75
votes
13
answers
44k
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If visible light has more energy than microwaves, why isn't visible light dangerous?
Light waves are a type of electromagnetic wave and they fall between 400-700 nm long. Microwaves are less energetic but seem to be more dangerous than visible light. Is visible light dangerous at all ...
- 1,090
10
votes
3
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Do human bodies give off a consistent but unique radiation/electromagnetic/energy signature?
Is there any facet of the energy emitted by a human body that is consistent and unique - like a fingerprint, but a signal that could be detected by a remote device?
- 209