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

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5answers
72 views

Dependence of Color of Light on Wavelength?

Recently i saw a question here which asked "what does the color of light depend on as we percieve it?".Now some members answered that if you see an object from any other medium it appears the same ...
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1answer
26 views

How does this RSSI vs Distance equation work?

I came across this equation in a research paper, and can't seem to make sense of it. Let me give an argument for why it doesn't make sense, and perhaps someone can tell me where my flaw is? $$ ...
4
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1answer
117 views

Why don't I see green flames more often?

I was just thinking today that I usually see red flame, and have seen plenty of blue flame, but not green. My naive presumption for coloration of flames would suggest that I would see more green, so ...
11
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1answer
295 views

How do higher-order optical chiralities look like?

The optical chirality of the electromagnetic field is a conserved quantity, analogous to the energy density, linear momentum density, and angular momentum density, which describes how chiral the EM ...
1
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1answer
67 views

What is meant by infinite wavelength?

1#When an electromagnetic wave propagates in a plasma, with increase in plasma density the phase velocity ($v=\frac{\omega}{k}$) of wave increases. So at cut-off point $k=0$, and phase velocity ...
2
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1answer
106 views

What is the physical nature of electromagnetic waves?

I've been trying to work out what the physical nature of electromagnetic waves is, since I reasoned that given electromagnetic waves have wavelengths that are given in distance units, rather than ...
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0answers
26 views

How does mass affect the range of a nuclear particle?

Heavy particles such as protons and alpha particles of certain energy will lose all their energies in a definite distance in a medium, and this distance is called the range. The range is the distance ...
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0answers
43 views

Will matter vibrating at THz frequencies emit light?

Much like a magnet creating an alternating current when slid through a solenoid, will matter that vibrates at 500 THz create lightwaves? Here we are talking about taking an object which doesn't glow ...
3
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0answers
49 views

c “Propagation” in Weber Electrodynamics [closed]

The telegraph model of Weber-Gauss, relying on Weber's electrodynamics, modeled instantaneous action at a distance of the electric scalar potential (Coulomb potential) manifesting as propagation of ...
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0answers
20 views

Radio wave propagation path loss coefficient below 2?

We did a series of measurements of radio wave signal strength. The setup was between stations on top of flat roofs of neighbouring houses (with line of sight). We are interested in the path loss ...
0
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0answers
17 views

Concerning Thomson scattering

In https://en.wikipedia.org/wiki/Thomson_scattering, the intensity of the scattered light is diminished by the factor $\cos^2(χ)$. Can this angular dependence also be derived with quantum mechanics ...
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1answer
65 views

Dipole antenna $E$-field direction

I was looking up dipole antennas on Wikipedia, among other sites. I came across this animation: and was wondering why there wasn't any field lines in perfectly vertical direction. In the case of a ...
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2answers
29 views

Can you use Fourier transformations (or other) to read multiple superimposed barcodes?

If you printed bar codes on tracing paper/acetate etc. and then positioned several in front of one another, could you extract the individual codes from the aggregate overlaid image? I feel intuitively ...
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0answers
146 views

How did Maxwell conclude that light is an electromagnetic wave? [closed]

I was looking at the answers for "Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?", especially the answer by NikolajK that references a Wikipedia article and the ...
1
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1answer
77 views

Why phase velocity of light is slower in a dielectric than vacuum?

Why does light speed suffer a reduction when it passes through a homogeneous dielectric medium? I know my math says so, i.e.- a highly polarizable ($\chi$) medium is associated with high $\epsilon$ ...
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1answer
37 views

Accelerating electric charge

We know that massive bodies attract gas clouds that become ionized and the resulting acceleration can emit very high energy photons. In a case where a proton for example is undergoing prolonged ...
-1
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1answer
103 views

If photons have mass then how can they travel at speed of light? [closed]

Anything that has mass must be slower than speed of light. If they are travelling at speed of light they must contain infinite energy which should be able to destroy everything, clearly thats not ...
1
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0answers
30 views

Confusion about radioactivity

The following question is from General Problems on Physics by I.E Irodov 6.220. Find the decay constant and the mean lifetime of $^{55}\operatorname{Co}$ radionuclide if its activity is known to ...
4
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2answers
107 views

Can wifi signal reception be improved by opening a door? [closed]

Use Case A wifi user is in a different room than the router. The computer is having a hard time connecting and receiving the wifi signal. Engineering Question Can the wifi signal from the router to ...
1
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0answers
59 views

Can TE and TM modes propagate together in a waveguide?

I recently came to understand the TE and TM modes. As it is defined that E=0 for transverse electric and vice-versa. I have a few basic questions in mind which I thought to ask in one thread only. ...
0
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3answers
84 views

FWHM increase with energy (gamma spectra)

Below I have two plots from a gamma spectrum which I've been analyzing. The first plot is between a low energy range, the second between a significantly higher energy range. It is clear that the FWHMs ...
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2answers
103 views

How is frequency related to kinetic energy?

Does producing higher frequency waves require more energy than their low frequency counterparts with same amplitudes? For example, in electronics, would a 500 kHz wave require higher voltage to ...
0
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1answer
36 views

Why aren't EM waves directionless?

I've seen some descriptions of electromagnetic waves of late, almost comparing the wiggling an electron (or any charge) to the disturbing of a water surface, and as a result waves are formed that ...
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2answers
126 views

Why don't objects radiate off all of their heat energy?

Imagine a solid box in deep space. Solids are as far as I know constructed by positive nuclei in some sort of coherent structure, with electrons orbiting nearby too. Both the nuclei and the ...
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2answers
69 views

What is electromagnetic radiation exactly? [closed]

What exactly is electromagnetic radiation? Other than the maths involved I'm not able to understand it at an intuitive level, can somebody please explain what it is?
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0answers
11 views

How do i calculate the “attenuation effect” that of a perforated aluminum sheet?

I am conducting an experiment test different configuration of perforated aluminum sheets. I am working with radio waves but i am having am hard time finding any equations or properties for this ...
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0answers
39 views

Poynting of EM field and group velocity

Could anyone please show me mathematically how the poynting vector of an EM field is always parallel to its group velocity? I do understand the physical reason why it has to be the case, but showing ...
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3answers
58 views

Emission of EM radiation from an electron

I have read about an electron making a transition between two energy levels and electromagnatic radiation will be emitted. The problem is how and why e.m radiation is emitted.
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1answer
68 views

Why do physicists use a positive sign for the Fourier kernel / outward propagating waves? [closed]

I am not a physicist but rather an engineer / mathematician, so I've always wondered why is it that physicists use the positive sign convention in the forward Fourier transform. That is, in all of my ...
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0answers
54 views

Index of refraction for travelling EM wave problem

Let $n_1$ be the index of refraction of the first medium and $n_2$ be the index of the second medium. When $n_2>n_1$, then for an incident angle of $90^{\circ}$ we get a refracted light at a ...
3
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1answer
207 views

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 ...
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0answers
31 views

Gaussian beam with its waist lying on medium boundary

For $z<0$ the medium is air and for $z<0$ the medium has refractive index $n$ The waist lies on the $z=0$ plane with radius $W_0$. What is the solution in the medium? I take the distribution ...
0
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2answers
43 views

Photons reflecting off matter

When photons reflect off matter, do they always lose momentum to the object? If they lose momentum to the object, that means they lose energy, and so their frequency should decrease. However, when we ...
0
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1answer
56 views

Emission of Characteristic X Rays

X-rays are emitted when high velocity electrons in an X-ray tube collide with a metal target. Some high velocity electrons on collision with the metal atoms cause an inner electron of an atom to be ...
23
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2answers
2k views

Is it (practically) possible for a large building to be a Faraday cage?

In my sophomore year of high school, my P.E. teachers kept on complaining about how phones didn't have a network connection in our gym, regardless of model, service provider, etc. A couple of feet ...
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0answers
26 views

How long does it take for space dust to stop irradiating energy?

I heard that space dust is detectable because it irradiates on the infrared part of the spectrum? Does this happen forever? Won't it stop after some millions of years? Does it have to irradiate until ...
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0answers
30 views

What is the pure form of energy? [duplicate]

What is the pure form of energy? Einstein in his energy mass equation derivation said that electromagnetic radiation is pure form of energy.
2
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1answer
27 views

Understanding hollow waveguides. What is $\lambda_g$ on the figure?

I am trying to understand the field distribution in waveguides. On the figure is $HE_{12}$ mode of hollow fiber. What is the $\lambda_g$ ? Is it $\lambda_g$ = $\lambda_0$ / $n_{eff}$. Does the z ...
2
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3answers
1k views

If UV radiation 1 cm away from the halogen bulb is equal to Sun's radiation, what is the level of radiation 1 meter away?

Halogen light bulbs emit some amount of UV radiation, and some sources consider them dangerous. Here it is written, that UV radiation (of certain types) from a particular halogen bulb was equal to the ...
2
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0answers
40 views

Electromagnetic wave and intrinsic impedence [closed]

The electric field vector of an EM wave in free space is given by $$\bar E= \hat y [A\cos{\omega (t- \frac{z}{c}})]$$ where $ \hat y$ is the unit vector along the Y direction. What will be the ...
0
votes
2answers
64 views

Why wasn't the theory that light's velocity depended on its source very popular?

Before special relativity, it was believed that light having a specific velocity meant it had to travel through something. My question is, why wasn't the idea that light depended on its source very ...
1
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1answer
59 views

Electric field vector in visualization of polarization of EM wave

When we were taught polarization at the high school level, we were told that during polarization, we should consider the EM wave being axially or planarly filtered (e.g. by a polarizing sheet with ...
0
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2answers
55 views

Defining charateristic of light wave?

"Light is refracted when it travels from one medium to another." Does the sentence show that light is a wave?
0
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0answers
39 views

EM wave frequency and photon energy

We know that a quanta of light of frequency f has energy hf. But when I consider a single photon there is no concept of "frequency of a wave" because there is no EM wave associated with it which ...
1
vote
1answer
34 views

Can we use a photon to use it as a changing field in an electric generator? [closed]

In an electric generator we use a changing magnetic field to create electricity. But what if we use a photon's oscillation of EM waves to generate electricity in a metal wire as we do in an electric ...
1
vote
1answer
71 views

Black Body radiation and Uv, x and gamma rays [closed]

Is the reason why UV, x-rays and gamma rays are non-existent on the blackbody radiation spectrum is because instead of the atoms present in the walls of the blackbody absorbing the energy, the energy ...
0
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1answer
46 views

What happens when the receiver of a parabolic antenna is covered by a metallic layer?

Out of curiosity I decided to conduct a small experiment and covered the receiver of the parabolic TV antenna with a metallic cylindrical food container without touching the receiver. It blocked the ...
17
votes
1answer
249 views

Should a superconductor act as a perfect mirror?

I have been told that metals are good reflectors because they are good conductors. Since Electric fields in conductors cause the electrons to move until they cancel out the field, there really can't ...
3
votes
2answers
191 views

Is there one all encompassing electromagnetic field? Or are electromagnetic fields separate and individually generated?

Many people have been using very confusing and sometimes contradictory language when describing electromagnetic fields and electromagnetic radiation. It's going to be hard to word this question so ...
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4answers
145 views

Why the electromagnetic waves propagate and do not stand still?

I know that the electromagnetic waves are alternating electric and magnetic fields. But I don't get why they can't stand still and alternate at the same point. I would like a logical and verbal ...