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

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320 views

Does a HDD ( Hard Disk Drive) emit radio waves?

While I was reading the "guide" of a HDD I had bought a while ago, I found that it might emit radio waves. I was wondering if that is true and why that happens?
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2answers
1k views

Why do electromagnetic waves oscillate?

I've been considering this question, and found many people asking the same (or something similar) online, but none of the answers seemed to address the core point or at least I wasn't able to make ...
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2answers
118 views

Electromagnetic radiation lenses

This will probably be a very basic question, but looking for a simple answers. What I know the visible light is a form of electromagnetic radiation with a defined wavelength. the full spectrum ...
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2answers
231 views

Is it physically possible to convert matter into the electromagnetic spectrum (specifically x-rays)? [closed]

I was considering the problem with teleporting organic matter, and was curious to know if I can use this to avoid killing anything I teleport?
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1answer
39 views

Diffraction from interatomic spacing

In diffraction from a single slit, we learn that the angular width of the central maxima, is given by $2\sin^{-1}\frac \lambda d$. For $d\approx \lambda$, the incoming wavefront should be spread to ...
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2answers
447 views

Does AC current produce EM waves?

Does AC current in simple wires produce electromagnetic waves? AC current entails very rapid changes in polarity and therefore the electrons in the metal will feel rapidly changing forces which should ...
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0answers
83 views

Edison effect for incandescent bulb?

I would like to ask a question on incandescent light. From the Thermionic emission (Edison effect), heated tungsten filament emits electrons that could be collected by an anode (like a foil ...
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2answers
508 views

Do electromagnetic waves always move in straight lines?

When we send an electromagnetic short wave to the sky, it reflects due to the ionosphere effects. But if we send it horizontally, is it correct that it moves around the surface of the earth, and if it ...
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0answers
208 views

How much energy does the most powerful supernova release in any form other than neutrinos?

I have read most of the supernova article on wikipedia, and there are a lot of numbers and different types of supernovae so I am confused. What I need to know is how much energy is released from some ...
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1answer
108 views

Polarisation of light is a wave concept or applicable to photons as well?

I have a very fundamental question. We explain polarisation of light assuming wave nature of light. Is it still valid if we assume light as photons? Or in other words, polarisation is a wave concept ...
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0answers
66 views

Problem with relativity of acceleration

In this answer http://physics.stackexchange.com/a/92833/36977 John said that acceleration is not relative in the general theory of relativity. But this is a problem: as we all know, accelerating ...
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7answers
594 views

Is the sun's solar radiance spectrum matching up with water's absorption spectrum just coincidence?

People frequently point out that water has a pretty narrow range in which it isn't very absorbing of light, reaching a minimum at a wavelength of about 500nm: And that our eyes have made good use ...
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1answer
90 views

Young's DS experiment and most light sources

The reason why two independent bulbs cannot be used to create the young's two slit interference pattern is that the phase difference between those two sources varies very rapidly and therefore, the ...
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0answers
44 views

Is it physically realistic to have an electric field and polarisation density but no displacement field?

Given a Lagrangian density that describes a classical dielectric in interaction with the EM field, I found the Euler-Lagrange equations, and in the case of the electric field, worked through to find ...
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1answer
88 views

When was it established light travels forever?

The range of electromagnetic radiation is indefinite. When was that established? Doesn't Hubble's limit have an effect?
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0answers
72 views

Hidden momentum

I'm trying to learn about hidden momentum. After reading what I could find with a google search, I understand that it is equal to the momentum carried by radiation, calculated with the Poynting ...
0
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1answer
57 views

What electromagnetic wave produces the strongest electrical current when making contact with an element?

More specifically, what electromagnetic waves can we utilize to generate electrical power and out of those waves, which one would produce the most power? Additionally, which one would be the most ...
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1answer
118 views

Can two spools shield you effectively against radiation

a friend of mine thinks that by buying a product called rayguard he can effectively shield against electrosmog. On the website, there are multiple evidences that this might work. However the product ...
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0answers
26 views

Electromagnet emitting light [duplicate]

We all know that (visible for human) light essentially is an electromagnetic wave with a frequency around 1/((any value between 380 and 760)*pow(10,9)) Hertz. So, if we will build (hypothetically) ...
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2answers
141 views

What would happen if an incredibly high energy photon passed through a human body?

What would happen if an incredibly high energy photon passed through a human body (or any other material)? When I say incredibly high energy photon, I mean higher than any known energy scales... ...
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2answers
142 views

Does the photon emitted by an electron falling to a lower energy level have a direction?

When an electron falls from an energy state to a lower one, electromagnetic radiation is emitted. Is this equally emitted in all directions (as a spherical wave) and can we only give it a direction ...
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3answers
3k views

Real and imaginary parts of dielectric constant vs refractive index?

So for a complex dielectric constant $\epsilon = \epsilon_a + i\epsilon_b$, the wave vector and index of refraction are related to it through $k = \frac{\omega}{c}n$ and $n = \sqrt{\frac{\mu ...
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1answer
88 views

What kind of damage is expected to happen to the earth in case of being hit by a direct gamma ray burst?

I understand how the ozone layer would be quickly depleted and the UV radiation from the sun would reach the ground...etc I understand all this, but what confuses me is where all this huge amount of ...
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1answer
768 views

Can electron exist as a standing wave inspite of successive superposition?

With the development of quantum mechanics, it was found that the orbiting electrons around a nucleus could not be fully described as particles, but needed to be explained by the wave-particle duality. ...
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1answer
66 views

Cause of radiation resistance

I was reading Radiation Damping and light scattering from Feynman's lectures on physics. The following excerpts are from chapter 32, Vol I What is this radiation resistance due to? Let us take a ...
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3answers
266 views

Can we explain Huygen's principle taking into account Maxwell's predictions?

Descartes gave the corpuscular model (1637) of light. Corpuscular model was further developed by Issac Newton. Model predicted that if the ray light (on refraction) bends towards the normal then the ...
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0answers
382 views

Vector and scalar potentials of plane wave

Consider a simplest 3D solution of Maxwell's equations: $$\vec B=\vec e_z \cos\left(\frac{2\pi}{\lambda}(ct-x)\right),$$ $$\vec E=\vec e_y\cos\left(\frac{2\pi}{\lambda}(ct-x)\right),$$ and ...
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3answers
170 views

Do electromagnetic waves have endpoints?

When learning about electromagnetic waves at school we never talked about any endpoints as we did with standing waves, so I assumed that light has an endless length, but that doesn't make sense. So my ...
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1answer
75 views

Is it feasible to transfer energy from power stations to communities via photons instead of electrons?

Electrical wires are relatively inefficient in transferring energy--especially when the place of production is quite far from communities. Would it be possible to transfer that energy via photons? I ...
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1answer
94 views

How is the orientation of an electromagnetic wave determined?

I was looking up for how polarisers work, I understood mostly everything except the part that explains that the polariser filters everything except light that is in a certain orientation. Here are my ...
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1answer
227 views

Would there be EMF induced in our body due to electromagnetic radiations?

The experiments of innovative Faraday and Joseph Henry in USA, conducted around 1830, demonstrated conclusively that electric currents were induced in closed coils when subjected to changing magnetic ...
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2answers
229 views

Why do light disappears the moment we switch off the source (inside the wooden box)?

I am failing to explain why light won't remain inside the wooden box in the following situation. I considered a wooden box closed from all the sides, with a bulb inside it. If we switch on the bulb, ...
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2answers
243 views

Derivation of Lagrangian density for an infinite classical dielectric in interaction with the EM field

I am tasked with reading and reproducing all the steps in J.J. Hopfield's 1958 paper "Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals". Embarrassingly I am stuck ...
11
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3answers
347 views

Does radio use virtual photons?

In radio communication each accelerated electron in the transmitter antenna interacts with an electron in the receiver antenna by exchanging a photon. Is that photon always a virtual photon as ...
8
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3answers
1k views

What is the relation between electromagnetic wave and photon?

At the end of this nice video, she says that electromagnetic wave is a chain reaction of electric and magnetic fields creating each other so the chain of wave moves forward. I wonder where the photon ...
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2answers
266 views

If photons don't interact directly, how can electromagnetic waves interfere?

If photons don't interact directly, how can electromagnetic waves interfere? I know that photons can scatter via higher order mechanisms, but not directly. Does those mechanisms explain the classical ...
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2answers
154 views

Do electromagnetic fields gravitate?

It's well known that electromagnetic fields contains energy but do they gravitate ? When we talk about the composition of the universe it's now accepted that the 74 % is dark energy , the 22 % is ...
2
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1answer
139 views

some questions regarding Doppler shifting versus absorption-emission

I just got in what I thought was a silly exchange where a self-identified physicist states that the difference between "red-shifting" (in the Doppler sense) and the re-emission of light at longer ...
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0answers
254 views

1-dimension radiation problem [closed]

A positive charge $q$ is fired head-on at a distant positive charge $Q$ ( which is held stationary ), with an initial velocity $v_{0}$. It comes in, decelerates to $v=0$, and returns out to ...
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1answer
422 views

Physical Interpretation of Poynting Vector

I'm looking for a physical interpretation of the Poynting Vector. I understand that it should be thought of as an energy flow due to the electromagnetic field, but would I be correct in saying that in ...
2
votes
3answers
212 views

What is the Bremsstrahlung or dipole radiation mechanism involved in the emission of radiation by the rotating or moving charge?

A rotating charge such as the electron classically orbiting around the nucleus, will constantly lose energy in form of electromagnetic radiation. I asked my teacher about how this radiation ...
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2answers
327 views

A difference between Plane Wave and Collimated?

Collimation is clearly in reference to ray($\vec{k}_{xy}$ vector) orientation unlike waterfront continuity( $\phi_{xy}$ phase shift) described by plane-wave. Not to say that one is not directly ...
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0answers
237 views

Questions about Michelson interferometer

I have been doing experiment on Michelson experiment, but I don't quite understand why white light results in an interferogram with very few fringes, and why are they necessarily Gaussian? I know that ...
5
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0answers
250 views

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?
3
votes
1answer
100 views

Do monochromatic waves carry information?

The answer is negative according to http://www.mathpages.com/home/kmath528/kmath528.htm It should also be remembered that a perfectly monochromatic wave carries no information, and therefore is ...
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3answers
70 views

Can radioactive energies become electromagnetic

I am trying to learn about radioactive energies and wonder if, because these also seem to come under the topic of radiation, can these energies become electromagnetic. I'm pretty much a beginner, so ...
14
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2answers
381 views

Do accelerated charges radiate or not?

This questions has been asked all over the net (here included) but I can't find a satisfactory answer or discussion. Some say it does not radiate if the acceleration is caused by a uniform gravity ...
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1answer
154 views

Can we draw analogy between em power flow through free space and ac power flow through a transmission line?

Knowing that the free space has a characteristic impedance (which is purely resistive, measured in ohms) I was wondering if I can model the free space as an infinitely long transmission line- ...
2
votes
1answer
98 views

Is there a physical reason why the detection pattern of microphones and antennas is a cardioid?

I was wondering if there's an underlying physical reason why detection in microphones and antennas is a cardioid, or if it's just that a cardioid happens to be the mathematical object that best ...
1
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2answers
561 views

Exciting Surface Plasmon-Polaritons with Grating Coupling

I'm very new the topic of SPPs and have been trying to understand this particular method of exciting surface plasmons using a 1D periodic grating of grooves, with distance $a$ between each groove. If ...