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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How strong are Wi-Fi signals?
My family members dislike the idea of having many devices communicating wirelessly in our house, arguing that the signals have negative effects on our physical health.
I would like to tell them the ...
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Why isn't my calculation that we should be able to see the sun well beyond the observable universe valid?
I recently read an interesting article that states that a human being can perceive a flash of as few as 5 or so photons, and the human eye itself can perceive even a single photon. The brain will ...
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What are the various physical mechanisms for energy transfer to the photon during blackbody emission?
By conservation of energy, the solid is left in a lower energy state following emission of a photon. Clearly absorption and emission balance at thermal equilibrium, however, thermodynamic equilibrium ...
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What's the physics behind XKCD #2027 (time between lightning flash and radio wave burst)?
XKCD usually has solid (and often contemporary) science behind it. Lightning Difference, #2027 one says:
Q: What’s that trick for telling how many miles away lightning is?
A: Just count the seconds ...
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Does a constantly accelerating charged particle emit EM radiation or not?
The Abraham-Lorentz force gives the recoil force, $\mathbf{F_{rad}}$, back on a charged particle $q$ when it emits electromagnetic radiation. It is given by:
$$\mathbf{F_{rad}} = \frac{q^2}{6\pi \...
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Why do prisms work (why is refraction frequency dependent)?
It is well known that a prism can "split light" by separating different frequencies of light:
Many sources state that the reason this happens is that the index of refraction is different for ...
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Do two beams of light attract each other in general theory of relativity?
In general relativity, light is subject to gravitational pull. Does light generate gravitational pull, and do two beams of light attract each other?
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Phase shift of 180 degrees of transversal wave on reflection from denser medium
Can anyone please provide an intuitive explanation of why phase shift of 180 degrees occurs in the Electric Field of a EM wave, when reflected from an optically denser medium?
I tried searching for ...
WhizKid
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Why and how is the speed of light in vacuum constant, i.e., independent of reference frame?
I was told that the Galilean relative velocity rule does not apply to the speed of light. No matter how fast two objects are moving, the speed of light will remain same for both of them.
How and why ...
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Cyclist's electrical tingling under power lines
It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...
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Why doesn't light affect a compass?
In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
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Do rainbows have ultraviolet bands and infrared bands?
We have seen that rainbows looks so colorful as we are only able to see only the visible light. But Do they also have ultraviolet bands and infra-red bands, that we are unable to see?
I know someone ...
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Scattering of light by light: experimental status
Scattering of light by light does not occur in the solutions of Maxwell's equations (since they are linear and EM waves obey superposition), but it is a prediction of QED (the most significant Feynman ...
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Can I use an antenna as a light source?
Can I use a normal metal antenna to emit visible light?
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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 ...
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