The photon is the quantum of the electromagnetic four-potential, and therefore the massless bosonic particle associated with the electromagnetic force, commonly also called the "particle of light". Use this tag for questions about the quantum-mechanical understanding of light and/or electromagnetic ...

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Shouldn't HDM drain photons energy?

Hot dark matter (HDM) would be made from very light, fast moving particles. Such particles could not possibly be gravitationally bound to any structure, but rather would be dispersed all across the ...
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23 views

When thermal IR gets reflected from an object, does it change its wavelength (frequency)

I'm working with thermal infrared (IR) cameras to detect human thermal radiation. I notice I can easily distinguish non-human objects throughout the camera's field of view, though all are at same room ...
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41 views

Number of photons through glass [closed]

I am getting mixed information on the total photon count involved with light transmission through glass. I'm not looking for percentages and I don't have equipment to count photons. For simplicity ...
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46 views

Exchange of virtual photons [duplicate]

How does the exchange of virtual photons as per QED explain the electrostatic attraction of particles of opposite charge?
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1answer
32 views

What is the difference between upconversion and two-photon absorption?

I thought that two-photon absorption is the underlying mechanism of upconversion, but according to Wikipedia (1, 2), Upconversion should be distinguished from two-photon absorption [...] and ...
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46 views

Particle nature of light [closed]

How particle nature of light can be observed in material world? To common man light does not hit them or make them fall when light beam is projected on them.
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86 views

What is a linear polarized photon?

According to Dirac a 'linear' polarized photon is a superposition of left and right rotating photons. Here is a puzzling aspect of this superposition. There are dichroic materials which can absorb ...
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Is the Poynting vector non-zero when two magnets are placed on either side of a charged capacitor? [duplicate]

I charge up a parallel-plate capacitor, and put a bar magnet on either side, such that the magnetic field is perpendicular to the electric field. S = E x B Do photons start coming out of the ...
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72 views

What happens to spacetime in a universe with no clocks?

For example, in the far future when all matter has been absorbed into BHs which have evaporated leaving only photons.
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141 views

Photon absorption by atoms vs compton scattering

In compton scattering, a photon may deliver only some of its energy to an electron. But when dealing with photon electron interaction in an atom, it's all or nothing. Why the difference? Also, ...
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25 views

Refraction Explanation From Particle Perspective

I was wondering if there was an intuitive way of understanding refraction from a particle perspective. By this I mean, that before entering a lattice, a photon has some momementum, it then enters at ...
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59 views

Do photons traverse through the vacuum of outer space as a helix? [duplicate]

I’m trying to understand “Electromagnetic waves”. If electromagnetic waves traverse as a helix then do photons traverse as a helix?
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1answer
70 views

Does light with opposite spins cancel out the probability of an event?

I'm an A level student and as i was reading QED by Richard Feynman, I came across something really interesting, that light can be reflected from all parts of the mirror according to the quantum theory....
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1answer
66 views

Where did all the photon energy go?

From the wikipedia page on dark energy, in reference to the total mass-energy of the universe: The mass–energy of dark matter and ordinary (baryonic) matter contribute 26.8% and 4.9%, ...
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how to see photons

I recently saw a couple of videos, in which you could visualize photons traveling through something (a bottle, for example). So my question is: how does it works? How can we see light if it doesn't ...
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2answers
88 views

Could we curve the flight path of a photon?

I was wondering about photon's interaction with matter, and why photons dont slow down. They seem to always bounce in a straight line at the same speed (I think), as if some force is charging them ...
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2answers
60 views

Probability of photon to photon collision

2 photons having sufficient energy can collide and form an electron positron pair (which then annihilate and form a new photon pair - with lower energy?). I assume this means that they can't collide (...
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2answers
123 views

How does the propagation of gravity work for photons?

As explained in the answers to this post, photons apparently exert a gravitational pull on other objects. It has also been explained on this site, that gravity propagates at the speed of light. I'm ...
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48 views

Could someone please answer these questions? [duplicate]

I have tried asking this question a number of different ways but I seem to keep messing it up. Please let me try another way. I know that the number of times a photon oscillates per second (it's ...
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1answer
59 views

What would happen if light was converted into matter as it is propogating?

If light is a form of energy and can be converted into matter then does light slow down since no mass full object can reach the speed of light
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2answers
61 views

Compton scattering by proton

I found only specialized articles on the subject, do you know of any accessible article explaining the laws governing a photon colliding with a proton? Would the same formula apply to the phenomenon ...
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1answer
92 views

Is double slit interference due to EM/de Broglie waves? And how does this relate to quantum mechanical waves?

I'm really confused about the fact that there seems to be two types of waves at play: the EM wave, which I understand to be an actual fluctuation of EM fields in space, and this other type of bulk "...
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2answers
207 views

How does light change directions? [duplicate]

To the best of my knowledge, light will always travel at the speed of light. How then does it get reflected and change directions? Wouldn't it have to decelerate, come to a stop, and then accelerate ...
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47 views

Photon Gas Stress-Energy Tensor

In standard texts it is typically discussed how one can obtain the stress energy tensor of a perfect fluid, in both coordinate-dependent and coordinate independent forms: \begin{equation} \mathbf{T}=(\...
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2answers
59 views

Photon emission between an electron and positron

If I placed and electron and a positron at a certain distance apart in a vaccumm, they would attract each other and annihilate producing 2 or more gamma rays. But, what I would like to know is, does ...
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1answer
48 views

Can two photons form a bound state?

I've always wondered if it's possible to bind two photons, in particular by gravitational interaction. Photons don't have a rest mass but nevertheless have a gravitational mass, by which they can ...
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Is the “number of photons” of a system a Lorentz invariant?

I'm wondering whether the number of photons of a system is a Lorentz invariant. Google returns a paper that seems to indicate that yes it's invariant at least when the system is a superconducting ...
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2answers
54 views

Can a laser beam be captured in prism?

is there a way to shoot a laser at a prism (or something) and have it glow when the laser hits it? I want to make a small box with a small hole in it. With the prism in the box, when the laser is ...
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How are photons influenced by gravity? [duplicate]

Are photons actually a zero-mass particle, or are they a low-mass particle. Ive heard many mentions of photons having no mass at all, but shouldnt the massive gravity of a black hole not affect light ...
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4answers
210 views

Why do we say that photons are particles? [closed]

This question may appear stupid but I really do have to understand. Maybe it's just semantic and nothing else. Why do we say that photons are (elementary) particles? They are pure radiation, since ...
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2answers
106 views

How does absorption of light by atoms and molecules work?

I found this question on a hobby science forum (mainly about chemistry) and found embarrassingly that I couldn't answer the question. A few searches along the lines of 'photons absorption' here on Ph....
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1answer
61 views

What is the affection of stress tensor of spacetime by the energy/mass density moment of a photon? [closed]

First of all what kind of moment exhibits the photon under its propagation to spacetime continium -quadrupole,dipole or monopole! Please, explain me- why. Do Give some arguements! When it propagetes ...
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3answers
76 views

If light slows down while passing through a material, does it speed back up while in a vacuum?

Light slows down while passing through, say, water. After passing through the water, does the light speed back up to the "speed of light"? If so, how and why?
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4answers
155 views

Does light in vacuum actually travel at the speed of light? [duplicate]

I know my question sounds like a joke (and I suppose on some level it is) but I'm confounded by the following: As the thought experiment goes, if I'm in a spaceship flying rapidly the people on earth ...
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131 views

Do photons generate gravitational waves since they affect with their energy the stress tensor?

The gravitational waves are fact. They are produced in a way predicted 100 years before by Einstein. Anything with energy affecting stress tensor of space time produces them. What does it happen with ...
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1answer
54 views

Change in momentum in a photon collision?

Let's say I drop a ball on the ground and it bounces up. According to classical physics, once the ball hits the ground it goes trough a short phase of deceleration until the velocity reaches zero, ...
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Formula for scattering and energy change of photons on (naked) nuclei

What is the formula for scattering and energy change of photons on (naked) nuclei? (On wikipedia Compton scattering does only explain scattering of photons by electrons, and I'm not even aware if the ...
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1answer
55 views

Light waves and water waves

I have an idea and i would like to have more information: If I drop a stone in the water some rings or waves will appear. Those rings are made of water and are behaving that particular way because of ...
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4answers
122 views

What carries electric field through space?

A stationary charge "creates" a constant (but not uniform) electric field around it, and a moving charge "creates" a variable electric field around it. What "carries" the information about the ...
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1answer
38 views

N-Body Simulation for Photons

For my undergrad optics class I am taking we have to select final projects to work on for second half of the semester. I have spent the last few weeks working on my own project which was a GPU ...
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1answer
51 views

Photon-Electron Interaction

Suppose a photon of energy 100 eV collides with a ground state electron of hydrogen atom. I know that the photon cannot give away a fraction of it's energy, and must be completely absorbed or not at ...
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3answers
162 views

How precise must the energies match for absorption of photons?

According to Quantum Mechanics, in order for an atom to absorb a photon the energy of the photon must be precisely that of a "jump" between energy states of the atom. How precise must it be? If I ...
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54 views

Generating Single photons

How can single photons be generated by making a coherent state weaker by attenuating it?(For reference please see, Quantum Computation and Quantum Information by Nielsen and Chuang, 10th edition,pg....
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Blackhole and light [duplicate]

I was talking with my friend about blackholes and I asked him "Why blackhole 'sucks' the photons?" He had no deeper understanding so he answered that "I dont know, may the light is affected, because ...
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1answer
28 views

In Rayleigh scattering, does a light wave cause the electrons (themselves), in a particle, to move at the same frequency as the incoming light?

The excerpt below, about Rayleigh scattering, is taken from the following page: https://en.m.wikipedia.org/wiki/Rayleigh_scattering Rayleigh scattering results from the electric polarizability of ...
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27 views

Is it possible to split a photon? [duplicate]

I read that if two photons collide than theoretically it would make light convert to matter. If you split a photon into two, will it convert matter into light? I'm a huge amateur so excuse me if this ...
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34 views

Electron and photon relation [duplicate]

While a photon is mass less but when it converts to an electron how mass can come into being ?
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80 views

Light absorption, reflection and transmission [closed]

I was bothered by some explanations in the internet about light. Can someone correct me or answer my questions regarding on how electrons react when hit by a photon in different situations: ...
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2answers
60 views

Photons can be regarded as particles?

So I've been reading an article and stopped at this sentence : "Likewise, we can take energy (such as particles of light, called photons) and turn it into matter." He gave an example of energy which ...
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2answers
116 views

Does light have mass? [closed]

Does light have mass? If yes, will it exert force? If no, then how are light particles are travelling at light speed? If light doesn't have mass how is it attracted by gravitational force (black holes)...