All Questions
Tagged with electromagnetic-radiation energy
164
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Magnetic and Electric energy for AC fields
In "Applied Frequency Domain Electromagnetics" (here the page) there are these two equations for the computation of the magnetic and electric energies stored in a certain volume $V_0$:
$$W_{...
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Standard formula for energy density of electromagnetic field
The formula for energy density of electromagnetic field in electrodynamics is
$$\frac{1}{8\pi} (\vec E\cdot\vec D+\vec B\cdot\vec H).$$
This formula appears in all general physics courses I looked at. ...
- 2,226
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If frequency is continuous shouldn’t energy be non-quantised?
If $E=hf$ and the frequency of electromagnetic waves is continuous (i.e. you can have frequencies of $1.5\ Hz$ or $0.3\ Hz$ for example) then surely energy isn’t discrete or quantized into because one ...
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What is the highest possible energy of a photon? [duplicate]
Are following suggestions ok to cap the energy of a photon?
When the photons have enough energy in a small enough volume to collapse into a black hole
When the wavelength of the photons becomes the ...
- 369
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How to get the formula of the energy of EM waves?
I am trying to get the formula for energy of EM waves:
$$W = \frac{E^2 + B^2}{2}$$ calculating the work done on a test charge by the force: $$\mathbf F = q(\mathbf E + v \times \mathbf B)$$ $\mathbf ...
- 16.7k
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Is mechanical energy conserved when charges accelerate?
Suppose we have two identical charges $q_1$ and $q_2$ and there is some distance $d$ between them. Imagine they are not allowed to move at first, but suddenly "we let them go". Then, they will start ...
- 1,183
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Interplay of energy between photon, electronic energy levels and kinetic energy
I can understand that atoms have quantized energy levels for its electrons, but an atom's translational kinetic energy is continuous. As such, why is the absoprtion spectrum not continuous? That is to ...
- 840
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Does a laser's listed wattage or joules include the frequency? Or just the amplitude?
In other words, if the number of photons in two different lasers is the same, but the second laser has a higher wavelength, does the second one have more 'wattage' or more total joules?
(Since higher-...
- 4,509
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How do you calculate intensity given the energy of a wave?
I’m a bit confused when it comes to calculating intensity versus energy of a wave.
If I’m given a wave with an energy of 1 eV, how do I calculate its intensity ? I know intensity is usually measured ...
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Does polarisation matter in double slit experiment?
So I am studying diffraction, in particular the diffraction of electromagnetic waves using a double slit set up. However, there seems to be no mention of the polarisation of electromagnetic waves and ...
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Why does work done by light not equal energy absorbed?
Question: Suppose a spherical particle of mass $m$ and radius $R$ in space absorbs light of intensity $I$ for time $t$. (a) How much work does the radiation pressure do to accelerate the particle from ...
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What's the energy of all the light/electromagnetic radiation in our galaxy?
I came upon this question while watching a pop-sci video on youtube about Dark Matter and thinking about all the things that could be contributing gravitational influence to a galaxy.
From relativity ...
- 133
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2
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Near-field energy transfer
If you absorb energy in the near field of the antenna, it will produce a loading effect on the source. Whereas in the far field it will not.
Is there an intuitive explanation why this is true for one ...
- 11
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How does light energy increase when passing through the ergo sphere of a black hole?
I watched a video recently about using the ergosphere of a spinning black hole as a source of virtually infinite energy by surrounding it with mirrors and shining electromagnetic waves in there. In ...
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Why the energy of electromagnetic waves is directly proportional to frequency whilst for mechanical waves this is not true?
The energy of a photon is directly proportional to its (angular) frequency:
$$
E=\hbar \omega.
$$
The energy of a classical mechanical wave is, however, proportional to the square of $\omega$:
$$
E=\...
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