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 ...

learn more… | top users | synonyms (1)

0
votes
0answers
45 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} ...
1
vote
2answers
56 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 ...
1
vote
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 ...
10
votes
3answers
224 views

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 ...
0
votes
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 ...
0
votes
0answers
12 views

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 ...
0
votes
4answers
203 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 ...
0
votes
2answers
99 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 ...
-5
votes
1answer
55 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 ...
0
votes
3answers
73 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?
2
votes
4answers
147 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 ...
7
votes
0answers
126 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 ...
0
votes
1answer
47 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, ...
0
votes
0answers
20 views

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 ...
0
votes
1answer
49 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 ...
5
votes
4answers
113 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 ...
1
vote
1answer
35 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 ...
1
vote
1answer
50 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 ...
5
votes
3answers
157 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 ...
0
votes
0answers
53 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 ...
1
vote
0answers
31 views

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 ...
0
votes
1answer
25 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 ...
0
votes
0answers
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 ...
-1
votes
1answer
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 ?
1
vote
0answers
67 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: ...
0
votes
2answers
59 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 ...
1
vote
2answers
113 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 ...
3
votes
3answers
110 views

Curious question about light and photons

If a photon wavelength (e.g., yellow) is isolated from the other wavelengths that the sun emits (once it gets to earth), can that particular particle/photon be distorted slightly into a wavelength ...
1
vote
2answers
79 views

How come lenses alter the path of photons?

From what I know, photons are theorized particles and believed to be massless (just energy) and travel at the speed of light. How come a lens, which is an object made of atoms, can bend a light path? ...
0
votes
0answers
46 views

The photon clock thought experiment

In reference to this video. If a photon clock moves away from us the photon will travel greater distance and therefore the clock will tick slower, so I would assume it will tick slower if it is ...
0
votes
1answer
21 views

Observe photons

Could they observe photons of light? Or is it so small for us to see? I think if we would come to know more about photons, and their motion and so its interaction with matter, we would understand more ...
1
vote
3answers
62 views

Photocurrent's dependence on frequency [duplicate]

Sounds like a rookie question, this, but could someone please explain to me why doesn't photocurrent increase when we increase the frequency of the incident radiation? I mean, an increase in frequency ...
0
votes
1answer
54 views

Can photons undergo quantum tunneling? [duplicate]

Most leptons can do this so I'm curious to see if photons or any bosons at all can.
3
votes
2answers
72 views

Time-coherency of “incoherent” light

Even "incoherent" light as the one of a light bulb has some coherency, and would interfer in the double-slit experiment (even if more blurry because the different wavelengths don't trigger the same ...
4
votes
2answers
141 views

Do the photons emitted along with the gravitational waves take more time to reach earth than the ones emitted after them?

I'm puzzled because the gravitational waves do warp the spacetime locally. They do it continuously as they propagate. So the photons travelling in tandem with these waves must be constantly following ...
0
votes
0answers
29 views

Is there a limit to the concentration of photons in a given volume?

If you have a given fixed volume, is there some physical limit to how many photons can exist in that volume?
0
votes
2answers
30 views

Compton Effect, why does electromagnetic radiation lose less energy when hitting particles with greater mass?

One of the problems in Rae's Quantum mechanics book, at the end of the first section, relates to x-ray's scattering off either an electron or a carbon atom. Using the equation given to you in the book ...
2
votes
1answer
12 views

How is the energy spectrum of a gamma ray in a material?

I'm trying to solve the following problem for a course in radiation physics. A thin ray of intensity $I_0$ and energy $E_0$ impacts in a material. What is the intensity and the energy of the ...
4
votes
4answers
160 views

How do they find the energy of a photon?

Is the actual energy of a photon ever measured? How is it done? I read that a photon is usually identified by diffraction, that means its wavelength is measured, is that right? In this way we ...
0
votes
2answers
34 views

Radiation pressure applied to different color surfaces

Does the value of radiation pressure exerted by photons from sunlight vary when applied to surfaces of a different color? More specifically, ranging from pitch black to white surfaces. Also, is ...
1
vote
1answer
87 views

Light is/produces a electromagnetic wave, but is the opposite also true?

A similar question has been asked, and to some extent the answer is: you need an antenna with $L \approx 200nm$. But it's not entirely clear to me if this is completely hypothetical, as "Marek" also ...
0
votes
0answers
17 views

How can I calculate the bipartition angle for photoelectrons produced by photoelectric effect?

I'm taking a course in radiation physics and I'm studying the photoelectric effect. In the notes that he gave us my professor states that half of the emitted electrons are emitted forward with an ...
0
votes
2answers
60 views

is photon direction affected by source velocity? [closed]

let's suppose the red ball in the below image is an object with V' velocity, the car and the surface travel in V (0.5 c). based on relative velocity laws, the red ball will hit the green pointer ...
3
votes
1answer
84 views

How many photons are there in free space on average

Estimates of the amount of for example "dark matter" are of interest to the cosmologists. However, I have never seen an estimate of how many "free" photons could be speeding about in the known ...
2
votes
1answer
71 views

Can an absorbed photon be emitted as two photons?

I am taking an intro to astronomy class, and have touched upon absorption and emission lines and etc, the prof asked this question in class and got me thinking. I would want to say no, because one ...
0
votes
1answer
82 views

Interpretation of time dilation

Is there any interpretiation of time dilation for photons? I mean, how does time work for them? Do photons have any distinction between their own and observer's time? Or is it something like ultimate ...
6
votes
1answer
105 views

Do stray photons become interstellar daggers to a space traveler near the speed of light?

Suppose I am traveling through space, accelerating closer and closer to the speed of light. As I speed up, photons traveling towards me become blue-shifted to higher and higher frequencies. When I am ...
1
vote
0answers
36 views

Is any photon really moving? [duplicate]

I read that when something moves at the speed of light, length contracts at the direction of motion. Now consider a photon traveling in the z axis. Since it is travelling at the speed of light, the z ...
0
votes
0answers
24 views

How do I mathematically treat a photon interacting with a potential?

(My background: PhD Student, have taken many quantum mechanics courses, but not QFT yet). Hello, In quantum mechanics for massive particles such as an electron, when the electron is in the presence ...
1
vote
1answer
97 views

Photon doesn't answer it… How will wave nature explain it?

There are two perfect reflect mirrors facing opposite to each other... I place a lamp which is not lit in between the mirrors... I switch it on and switch it off and remove the lamp from between the ...