0
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0answers
30 views

Energy in an electromagnetic wave

A radio antenna creates EM waves through switching the polarization in the antenna at a certain frequency. I assume the the energy of the photons produced in this process amount to E=hf for each ...
1
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1answer
70 views

Is every electromagnetic radiation considered “light”?

Somebody mentioned on Freenode chatroom for physics that All Electromagnetic Radiation are delivered in form of Photons not just light. Is it true? Does that mean if we get a THF electrical ...
2
votes
2answers
80 views

Suppose a light wave with wavelength 3m. What happens if one tries to contain that wave within a 1m container?

Suppose a light wave with wavelength 3m. What happens if one tries to contain that wave within a 1m container? If I'm going about this entirely the wrong way or have wrong conceptions about light ...
0
votes
1answer
38 views

What is the significance of the difference in the eigenvalue equations of Bloch functions for electrons vs photons?

any text on photonic crystals will highlight the almost perfect analogy between electrons in a periodic potential and photons in a periodic dielectric. The analogies are: $$V(\vec r + \vec R) = ...
3
votes
2answers
129 views

What is the energy distribution of light if it has an infinite length?

What is the energy distribution of light if it has an infinite length? I have read in one of the answers here on phys.SE that light has actually an infinite length. But then what is the energy ...
3
votes
1answer
214 views

What force particle mediates electric fields and magnetic fields?

The force carrier for magnetic fields and electric fields are supposedly photons. I don't get it: 1) Wouldn't that mean that a charged particle (e.g. an electron or even a polarized H2O molecule) ...
1
vote
1answer
178 views
1
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1answer
194 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 ...
1
vote
1answer
77 views

How do virtual-photons curve in a magetic field?

From what I understand photons only move in straight lines unless reflected or refracted (other than influences from gravitational fields and their usual wavelike movement). And since they are a ...
8
votes
2answers
329 views

No magnetic dipole moment for photon

Electrically neutral particles such as neutrinos can have nonvanishing magnetic dipole moments. Spin-1 particles, e.g., deuterium nuclei, can also have dipole moments. Googling seems to show that the ...
3
votes
2answers
307 views

Electromagnetic Momentum

My book says : The fact that electromagnetic radiation of energy carried momentum was known from classical theory and from the experiments of Nichols and Hull in 1903. This relation is also consistent ...
2
votes
1answer
195 views

Can a force stop a Photon since Photons have momentum and What does momentum mean when talking about massless particles?

Momentum measures how hard it is to stop an object. While Photons are massless they still have relativistic mass and energy. My question is can something stop photons other than being absorbed by ...
0
votes
2answers
123 views

Is it possible for a photon to be at rest? [duplicate]

I know it doesn't really make sense if looking at the photon from the wave point of view, but is there any law of physics which prohibits a photon from stopping completely? Thanks.
0
votes
1answer
51 views

Photon propagation direction prediction possible after interacting with neutral hydrogen?

My current line of research deals a lot with hydrogen's Lyman-alpha emission and subsequent interactions of the Lyman-alpha photons with the surrounding hydrogen gas. My question is whether ...
2
votes
1answer
1k views

Where is the amplitude of electromagnetic waves in the equation of energy of e/m waves? [duplicate]

Does the amplitude of the photon oscillations always stay constant and if it is not - what are the physical differences between the photon with higher amplitude in comparison to the one with the less ...
0
votes
1answer
92 views

EM Waves Energy Loss

Where does the energy go when two photons interfere destructively at a point on a screen in Young's double slit experiment ?
10
votes
1answer
306 views

How the inverse square law in electrodynamics is related to photon mass?

I have read somewhere that one of the tests of the inverse square law is to assume nonzero mass for photon and then, by finding a maximum limit for it , determine a maximum possible error in ...
4
votes
2answers
927 views

Do protons exchange photons with electrons?

I'm sorry for this question but, I just don't get it. According to the electromagnetic field theory, electrons repel each other by exchanging photons. How do protons attract electrons, by photon ...
3
votes
1answer
112 views

Absorption cross section for direct dissociation and predissociation - Photoelectric absorption

Why the absorption cross section in direct dissociation process is wide and structureless while the absorption cross section in the predissociation process is structured and containing lines which are ...
5
votes
4answers
2k views

Collision of two photons

Could someone explain me how will be look like collision of two photons? Will they behave like: Electromagnetic waves, they will interpher with each other and keep they wave nature Particles and ...
0
votes
1answer
170 views

Thermionic emission and delayed emission

I want to understand the concepts behind the thermionic emission. In thermionic emission, the energy randomization occurs and the energy may be split to electronic or roto-vibrational states. If this ...
3
votes
2answers
196 views

What is a photon's speed inside a dieletric?

We know that EM waves are slowed down in a dielectric. But at what speed does the photons that make up the wave travel? Do they always travel at the speed $c$, but colliding/being absorbed and ...
1
vote
1answer
629 views

How photons move along with EM wave?

So the wave moves like. a wave, it moves up and down, up and down. But how do photons move? Do they follow the same path or do they just go straight forward without oscillating?
2
votes
1answer
190 views

Does the electromagnetic field “spin”?

Due to electron "spin", a small magnetic field is produced. Maxwell's equations imply that magnetic fields are due to changes in electric fields. Is the magnetic field produced then because the ...
6
votes
1answer
429 views

Why is there a photon every millimeter on earth coming from a star millions of light years away?

I've been having this confusing thought for so long now it would be amazing if someone could answer me. Imagine this asterisk * . As you see, from the center point, lines go outwards, just like a ...
2
votes
3answers
524 views

If electromagnetic fields give charge to particles, do photons carry charge?

As I understand these two statements: An electromagnetic field gives particles charge A photon is a quantum of electromagnetic field It must mean that a photon carries charge. But I guess it isn't ...
2
votes
2answers
562 views

Frequency and wavelength of photons

I try to better understand how electromagnetic radiation works. So I have some questions. If an antenna emits at 100MHz (the charges on the antenna oscillate at 100MHz) what frequency will have the ...
2
votes
2answers
427 views

Electron model under Maxwell's theory

I was not able to recall my memories, so: What is the formula that states the frequency of electrons revolving around nucleus is equal to the frequency of light (or photon) emitted (or radiated)? (I ...
3
votes
3answers
2k views

What are electromagnetic fields made of?

I am trying to understand electromagnetic fields so I have two question related to them. What is a electromagnetic field made of? Is it made of photons / virtual photons? How about a static electric ...
2
votes
1answer
160 views

Can unbound electrons jump energy levels?

If an unbound electron (or indeed any charged particle) is moving through free space, is there a probability that it can spontaneously change energy by emitting a photon, or does this require the ...
4
votes
3answers
591 views

Is photon emission possible without electrons changing energy levels?

Does molecular vibrational transition and consequent emission of infrared radiation involve electrons changing energy level? In wikipedia, about vibronic transitions it says "Most processes leading to ...
2
votes
1answer
178 views

For someone who only studied electromagnetism, what is the modern way to explain electromagnetic fields?

After reading most of the electromagnetism chapters of Feynman's lectures on physics, I would like to understand in more detail, at least an idea, of what causes the electromagnetic fields. Not sure ...
1
vote
1answer
142 views

The energy carried from one winding of a transformer to another, in quantum terms

I have read in wikipedia this statement "The energy carried from one winding of a transformer to another, in quantum terms is carried by virtual photons, not real photons" (wikipedia src: virtual ...
4
votes
1answer
345 views

Question about Rayleigh scattering

To quote from Wikipedia on elastic scattering, "In this scattering process, the energy (and therefore the wavelength) of the incident photon is conserved and only its direction is changed." How does ...
4
votes
1answer
129 views

Photons in a “wrap-around” universe

This question was inspired by: How are photons "consumed"? Imagine I have some number of photons, $N$, each of frequency $\nu$, moving randomly in a spherical "wrap-around" universe of ...
5
votes
2answers
126 views

Photon absorption

[sorry, this way below the level of this forum -- flames are most welcome] When a photon is absorbed by a piece of matter that does not reflect it -- where does the photon "go"? Eg, one shines light ...
3
votes
3answers
146 views

Distant bodies emitting photons

This comes from a discussion forum, where a friend of mine asked the following: We can see objects in space billion of light years away, right? I started wondering about that. If you take 2 ...
3
votes
5answers
567 views

Particles, waves and parallel wire filters. Transmission formula?

If I think of a photon as a particle, I think a parallel wire filter should transmit proportionally to the uncovered area. (and reflect proportionally to the covered area). Obviously polarization ...
6
votes
3answers
2k views

Do mirrors increase the amount of light in a room?

So if you have a light bulb in a room, and you had a tool to measure the amount of light that's in the room, then let's assume the amount of light only caused by the bulb is "1" If you place a mirror ...
3
votes
3answers
1k views

How is electromagnetic wave variation distributed in space?

Imagine an electromagnetic wave (a monochromatic one for example) The electric field amplitude, and its variations travel in the propagation direction. So, if there really exists a propagation ...
12
votes
3answers
2k views

The exchange of photons gives rise to the electromagnetic force

Pardon me for my stubborn classical/semiclassical brain. But I bet I am not the only one finding such description confusing. If EM force is caused by the exchange of photons, does that mean only when ...
19
votes
4answers
1k views

What is the mechanism behind the slowdown of light/photons in a transparent medium?

So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the ...
15
votes
8answers
4k views

What equation describes the wavefunction of a single photon?

The Schrödinger equation describes the quantum mechanics of a single massive non-relativistic particle. The Dirac equation governs a single massive relativistic spin-½ particle. The photon is a ...
18
votes
5answers
2k views

How are forces “mediated”?

I hope this is the right word to use. To me, these forces seem kind of fanciful (except for General Relativity and Gravity, which have a geometric interpretation). For example, how do two charged ...