# Tagged Questions

Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.

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### Why aren't superconductors shiny? [duplicate]

Superconductors are really good at conducting electricity. Should they not reflect light very well too?
443 views

### Can I call additional conditions on potentials a Gauge choice?

Let's say I have an electromagnetics problem in a spatially varying medium. After I impose Maxwell's equations, the Lorenz gauge choice, boundary conditions, and the Sommerfeld radiation condition, I ...
574 views

### Why is laser light a cone?

What about the production of laser light disallows it to be perfectly straight as opposed to a cone? I feel like it should be a plane wave, not a very tight cone.
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 \... 3answers 258 views ### How “things” radiate electromagnetic radiation? [closed] How things radiate electromagnetic radiation? I don't ask why they radiate (higher temperature than 0K) but how they radiate this electromagnetic waves? 2answers 379 views ### An Electromagnetic Paradox? The above diagram represents an isolated system with two masses M, at position X, and m, at position x, connected together by an extended spring. Each mass is connected by rigid rods to ... 1answer 386 views ### home made atom destruction unit [closed] Today we learnt at school that atoms can be destructed. I believe Physics is a great science to do experiment and I would like to try it at home. 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I encountered a thought provoking article suggesting that electrons are electromagnetic waves. Is this possible? I may not agree with their entire model, but surely there is the possibility that an ... 1answer 286 views ### Are multipole fields, multipole expansion, and multipole radiation the same thing? Interaction between electromagnetic radiation and nuclei can be written in terms of multipole radiation. Are multipole fields, multipole expansion and multipole radiation the same thing? I have found ... 2answers 441 views ### Conceptual doubts in EM waves and old quantum theory [closed] I have a few questions. I know that EM waves transfer energy. So when they are generated why do they form curves? Are energy packets moving in a curvy path, or energy packets (quanta) not considered ... 1answer 773 views ### How much does sunlight affect inside temperature? Suppose we have a 3\cdot 3\cdot 3\,m^3 room of which one side is glass. And suppose that the other 5 sides have no effect on temperature (super isolation). We know from physics how to calculate ... 1answer 209 views ### Electromagnetic waves produced by a charged pith ball Maxwell’s equations appear to have no limitation as to the length of an electromagnetic wave that can be produced by an accelerating electric charge. So in theory, if I use a charged rod to oscillate ... 3answers 545 views ### Polarization of the lowest mode of a Gaussian beam Most introductory analyses of Gaussian beam optics work within Helmholtz scalar optics, and therefore they ignore the beam's polarisation. Because of that, I'm not clear on what are the possible ... 2answers 427 views ### Black body radiation I have a few questions related to the emission of electromagnetic radiation by black bodies. Consider the following image: On the above image I have drawn the rays of light that are emmited by ... 1answer 409 views ### Photons: Collection of Wave Packets that produce a plane wave Is it possible mathematically for photons, which behave as individual Gaussian wave packets, to combine in such a way that the approximate result is a plane wave at one particular frequency (i.e., the ... 4answers 948 views ### Origin of Rayleigh scattering Is Rayleigh scattering simply the elementary result of scattering theory, that, at low energies (long wavelengths) the scattering is dominated by s-wave scattering? 1answer 615 views ### Simple Question: Speed of Electromagnetic Waves in a Medium If the speed of an electromagnetic wave in a particular medium is such that v = c, the speed of light, does this mean that the permeability \mu = \mu_0, i.e. that of a vacuum and the index of ... 1answer 3k views ### How could we see microwave radiation with our eyes? A few years ago I read a short little article about how big our eyes would have to be to observe microwaves (or any long-wave radiation for that matter). I don't remember enough about the article, or ... 1answer 911 views ### Does an accelerating proton also lose mass? A proton accelerated with electric field gives off E.M. radiation and therefore should lose mass. Larmor's formula gives us a value for the power emitted (varies as acceleration squared). However, as ... 1answer 122 views ### Astronomical-wavelength radio (AWR) transmissions between cosmic plasmas? My son asked me if electromagnetic waves longer than radio exist. I told him that even though physics permits such waves, there are no antennas long enough to radiate or detect them. However, on ... 1answer 155 views ### Interaction of an electromagnetic wave with a two level system in the domain of quantum field theory Suppose I shine an electromagnetic wave on a two-level system. I need to describe how the system evolves in context of quantum field theory i.e. using a quantized EM field in the problem. The first ... 3answers 210 views ### Are waves on water an example of gauge invariance? So: Is the close similarity of small waves crossing water of varying depths ("depth potentials") an example of an approximate gauge invariance? If so, do other "only the surface dynamics matter" ... 1answer 155 views ### How can we observe lights properties if it travels at the speed of light, or can we? [duplicate] Special relativity says that anything moving (almost) at the speed of light will look like its internal clock has (almost) stopped from the perspective of a stationary observer. How do we see light as ... 1answer 442 views ### Super High Frequency Electromagnetic Radiation - String Theory I am a serious high school student with one year of physics class experience, so please point out if there are any flaws in my question or reasoning. Thanks! Gamma ray radiation possesses a ... 4answers 8k views ### 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 ... 2answers 3k views ### Why is the photon emitted in the same direction as incoming radiation in Laser? When an atom “lases” it always gives up its energy in the same direction and phase as the incoming light. Why does this happen? How can this be explained? How does the photon generated because of ... 0answers 124 views ### Historical aspect of wave theory of light Huygens thought light as a wave. Wave is a propagation of physical disturbance. We now know that light is electromagnetic field. Electric and magnetic field fluctuates here. What Huygens really ... 2answers 23k views ### How and why does accelerating charges radiate electromagnetic radiation? Lets consider it case by case: Case 1: Charge particle is at rest. It has electric field around it. No problem. That is its property. Case 2: Charge particle started moving (its accelerating). We ... 2answers 1k views ### If light rays obey to the wave equation, why can they be thought as straight lines? I'm a newbie with physics but I'm wondering how a ray of light can essentially be represented. I have always known that a ray of light proceeds in a straight line until it encounters another object (... 4answers 5k views ### Radio antennas that are much shorter than the wavelength From my limited experience with ham radio when I was a kid, I expect transmitting and receiving antennas to have lengths that are on the same order of magnitude as the wavelength, and in fact I recall ... 5answers 6k views ### Why doesn't light kill me? Why does each individual photon have such a low amount of energy? I am hit by photons all day and I find it amazing that I am not vaporized. Am I simply too physically big for the photons to harm me ... 0answers 30 views ### Does quantum mechanics depend solely on electromagnetic waves? [duplicate] I am beginning to learn quantum mechanics. Since determining the position of an object involves probing by electromagnetic waves and since i have read a simple derivation of Heisenberg's uncertainty ... 1answer 291 views ### Effectivness of a metallic wall against microwaves propagation I would like to know how good or bad behave a metallic wall in stopping the propagation of an microwave signal. To be practical, let's take the example of a GSM relay antenna. If I set up the ... 4answers 10k views ### How can we detect X-rays? I know that X-rays can be detected by various ways, like ionizing of air particles. Is there a way to detect X-rays,which are photons, by detecting? Can something absorb the energy of the X-rays and ... 2answers 136 views ### Energy in Electromagnetic Waves Looking at diagrams of Electromagnetic Waves, it would appear to me that at certain times the waves have zero amplitude, and consequently zero energy. Indeed, substituting in the sinusoidal terms into ... 1answer 128 views ### Trying to understand EM wave and photon When electrical fields and magnetic fields couple together, it forms electromagnetic waves. And we can "quantized" it and see each "package" of it as photon. So can electrical fields and magnetic ... 2answers 269 views ### Is light's path a wave? In a lot of textbooks I see a schematic of light drawn as a squiggly line. I have even heard that some things are too small to be seen because they are smaller than the wavelength of light (and ... 2answers 1k views ### MRI's and Electromagnetic Radiation If the waves in an MRI can go through our body, why is it that light with its magnetic fields gets stopped at our skin? 0answers 390 views ### Mathematical equivalence between Liénard-Wiechert potential and 4-potential in Rindler coordinates I'm studying the problem of the radiation of an uniformly accelerated point charge:$$x^{\mu}(\lambda)\to(g^{-1}\sinh g\lambda,0,0,g^{-1}\cosh g\lambda) I found that when a point charge is moving ...
Is the de Broglie (matter) wavelength $\lambda=\frac{h}{p}$ of a photon equal to the electromagnetic wavelength of the radiation? I guess yes, but how come that photons have both a matter wave and an ...