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

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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 ...
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1answer
85 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 ...
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48 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 ...
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264 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 ...
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2answers
198 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
149 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 ...
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56 views

What mechanism can we use to convert waves energy?

In term of renewable energy, can we use waves as another energy that can be stored and used instead of solar, wind and etc ? What I mean here is not sea waves but another kind of waves such as radio ...
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1answer
76 views

What role does wavelength play in the identity of a photon? [duplicate]

According to this question: What determines color -- wavelength or frequency? It is the energy, and thus the frequency of a photon $E=hf$, that determines where it lies in the electromagnetic ...
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4answers
139 views

reproducing double-slit experiment with sunlight

Is it possible to reproduce Double-slit experiment at home with sunlight probably in a larger scale? Thanks for all the answers (and special thanks to Chris for the effort),so i understand that it ...
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2answers
122 views

Maxwell equations and quantized electromagnetic field

When the electromagnetic field is quatized for a single mode, we first take Maxwell equations and proceed to write the electric and magnetic field as a stationary wave, since we consider the ...
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27 views

How does a dynamic electric field change a semiconductors carrier mobility?

Can an electric field that is spatially and/or temporally dynamic affect the carrier mobility in or on a semiconductor and, if so, how and to what degree? I appreciate any help or thoughts you have ...
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122 views

Why bremsstrahlung occurs only with the nuclei? Why not with the electrons?

In many books I read that bremsstrahlung effect (for e+) only occur when the electron goes near the atomic nuclei. Why is not possible when cross near an atomic electron? Thanks,
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39 views

magnetising the material using coil

I studied that when alternating current is passed through the coil ,the coil produce magnetic field (primary) as shown in figure,when any conducting material placed near to that field, eddy current ...
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131 views

how do photons move with respect to EM (I'd like to picture wave magnitudes frame by frame) [duplicate]

(I'm aware treating photon as particle and talking about its position is not exactly, conceptually right but I think it makes sense, at least in the point of view of a beginner. Please just assume ...
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41 views

Power and frequency of photons and its relationship with biological safety

I understand that x-rays are more dangerous than radio waves because they are of higher energy, since they have higher frequency. However, it’s less dangerous to stand near a radio station with a ...
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1answer
83 views

Can one make a propagating field along a waveguide only have longitudinal/transverse components?

We know that in free space, a propagating electromagnetic wave is always transverse. However, along a dielectric waveguide, the propagating wave can have longitudinal components. The exist of the ...
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1answer
95 views

Finding the range of frequencies to which a receiver should be set

I'm working on a study guide for a test for my Modern Physics class, and ran across a question I'm having trouble with. A radar transmitter emits a pulse of EM radiation with ...
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1answer
46 views

Interactions of light with the air

This is an interesting thought which I had when driving home today looking in my wing mirrors. If you are driving a car and looking in your, say, right wing mirror, you see an image of the car ...
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40 views

Could there be ways to form hypergiant stars, quasars or supermassive black holes at the beginning of the Dark Ages?

Original title: Heat loss in collapsing parcels of gas or weak plasma at the beginning (not the end) of the cosmological dark ages Star formation from collapsing parcels of primordial gas in the late ...
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4answers
88 views

the relation between frequancy and energy of EM waves

In quantum theory, $$E=\hbar w$$ In classical theory, we have the Poynting vector: $$\vec{S_\space}=\frac{1}{\mu_0}\vec{E_0}\times\vec{B_0}{\cos}^2(kr-wt)$$ given S is energy flux density (the ...
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0answers
29 views

How to mathematically model a realistic aperture illumination?

I want to know a mathematical expression that I can use to model a realistic aperture illumination to produce the primary beam of an antenna so that the radial distribution of this aperture ...
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1answer
32 views

Rotation of polarization through optical activity

When a vertically polarized beam of light is incident on an optically active substance and rotated through some angle $\theta$, how is the degree of rotation related to the length of the path through ...
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0answers
41 views

Can an electron in empty space to create electromagnetic radiation?

Is it possible in the empty space to create electromagnetic radiation from oscillations of the charges only of one kind - positive or negative? This question stems from the fact that all man-made ...
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62 views

Distribution of current, charge and EM radiation from a centrally AC fed ball-shaped antenna

As far as I can understand, it is generally accepted that every classical electromagnetic phenomena can be explained by five equations: Maxwell's four equations and the Lorentz force law. However you ...
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1answer
112 views

Bohr atomic model: does the electron fall?

I know this is a classical system, and thus not compliant with the quantum nature of real atoms. But please bare with me. I have heard this before: the orbiting electron should radiate in the ...
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1answer
131 views

Why is communication lost in lifts?

Why is communication lost in lifts and cellars? For example, If I want to phone to someone, there is no signal communication in lift. Who may explain it?
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67 views

Is a longer antanna better for reception ? Or just more directional?

Let's say I have two antennas, A1 and A2, and they have identical radiation profiles. So the relative radiated energy in a given direction is the same for both antennas. Let's assume also that we ...
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39 views

Electron in an accelerating frame - a paradox

Suppose I am at point $a$ and I have an electron at rest at point $b$ some $r$ distance away. Say that I suddenly start spinning clockwise about my point $a$ at some constant angular velocity ...
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1answer
55 views

Why we do not consider trajectories for photons/lightlike curves/radiation? I am having a term confusion

Lately I have asked a question about the trajectory of photons and almost everyone told me that I shouldn't talk about trajectories. Also people talked about photons, lightlike curves, light, ...
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1answer
61 views

How far will a 1Hz EM Wave propagate if it's source oscillator is running for exactly one second? [closed]

If you have an Oscillator set on 1Hz and you let it run for exactly one second connected to an Antenna , how far will the generated EM Wave travel ?
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17 views

Will it produce alternating magnetic field with respect to time, if l hybrid soft magnet with self decaying(Radioactive) material?

Radioactive material emits electromagnetic waves (Gamma Ray). Soft magents has low magnetic coercivity, Right. Suppose if i hybrid very soft magnet alongside with strong radioactive material, will it ...
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2answers
84 views

Particles radiating energy when accelerating?

Let us say we have a charged particle moving in the positive $X$ direction with velocity $v$. If we give the particle a nudge in the $-X$ direction causing it to decelerate. Then from the saying ...
21
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3answers
2k views

Looking at the sun through heavy fog, do invisible wavelengths get through?

This morning it was particularly foggy and my son was excitedly looking at the sun through the fog, since of course he normally can't look directly at it and see the disk. I told him to stop looking ...
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1answer
554 views

Do photons decay as they travel in free space

From maxwell's equations, it occurred to me that photons are stable. Decrease in electric field creates magnetic field and vice versa and somehow there is a harmony that allows photon to exist as long ...
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1answer
44 views

What information do we lose when we increase whale songs to our hearing range?

TV documentaries on marine life often feature the evocative sounds of whales communicating with each other (apparently), over very long distances. The frequency of baleen whale sounds ranges from 10 ...
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Why spurious pulses are likely in partial discharges?

My notes The gas multiplication in the proportional counters is based on the secondary ionization created in collisions between electrons and neutral gas molecules, resulting in some visible ...
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1answer
184 views

Intersecting Lasers

What happens at the point of intersection of 2 lasers. If 2 lasers of different colour intersect, what will be happening at the point of intersection? Won't colour mixing happen?? Won't that point ...
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4answers
4k views

How far out from the Sun is visible light still sufficient to read a book?

Recent pictures from the New Horizons spacecraft, shown below, seem to indicate that, at Pluto's distance, we are entering a twilight zone, with a distinct lack of colors, although that could be due ...
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1answer
276 views

What is the origin of blackbody radiation? [duplicate]

Of course I know what black-body radiation is, like everyone else who has taken a thermal or statistical physics course. But it was recently pointed out to me that one thing that is rarely taught ...
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1answer
180 views

Near Energy In the Null of a Hertzian Dipole

Since $\mathbf E = -∇Φ - ∂\mathbf A/∂t$ one expects an oscillating $\mathbf E$ field even in the null of a Hertzian Dipole unless the two right hand side terms cancel -- which they do in the far field ...
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1answer
133 views

Why does the laser change colour? [duplicate]

In the first image, the laser colour is green. When it is shined on the plastic cap of the pink highlighter, the colour changes, why has this happened? Tech Details about the Laser Source are; Max ...
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2answers
113 views

Gamma spectroscopy - Do annihilation photons produce a backscatter peak?

Below is a diagram of part of a structure which I find in a gamma spectrum taken from a hall in which a neutron source is undergoing spallation. The structure which I'm interested in can be seen ...
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61 views

Generation and propagation of EM waves

How EM waves are generated? How do EM waves travel in space? like in many text books they have given an electric field sine wave perpendicular to magnetic field sine wave....is it exactly like that??? ...
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1answer
92 views

If electromagnetic waves can be generated by oscillation of a coil why can't light? [duplicate]

I was recently reading how electromagnetic waves are generated using oscillation of a current in an antenna. Why is it that this principle cannot be used to generate light?
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2answers
94 views

Electromagnetism and a simple doubt [duplicate]

Why don't electromagnetic waves need a medium to propagate? How does light get such a magnificent velocity?
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1answer
491 views

Gamma spectroscopy - Table of radioactive isotopes with gamma energy search

For anyone doing gamma spectroscopy by hand, the task is considerably eased by tables like this: http://nucleardata.nuclear.lu.se/toi/ Where not only can you search for particular nuclides, but you ...
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51 views

Gamma spectroscopy – What is this structure?

What is this strange structure in the gamma spectrum between 450 and 550 keV (below) around the peak at 477 keV? The spectrum seems to rise to a plateau (almost like a small Compton plateau) around ...
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1answer
245 views

What wavelength of light is the least absorbed by water?

As I understand it, an infrared laser range finder will not work underwater because the infrared rays are heavily absorbed by water. What wavelength (optical, ultraviolet, microwave, etc.) of light ...
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1answer
56 views

Is reflection actually due to very low critical angle?

When we take an example of a plane mirror, does the reflection occur because the critical angle for the silvered surface is very small? Are all the good reflectors good at reflecting because their ...
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53 views

Coincidence summing in gamma spectrum

Question on coincidence summing here. I've been reading about the coincidence summing effect when a radionuclide has two energy levels that decay to another state in rapid succession. There is also ...