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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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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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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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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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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61 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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72 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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95 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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210 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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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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63 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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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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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
223 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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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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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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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
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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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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
58 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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58 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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128 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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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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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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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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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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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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29 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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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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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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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)...
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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 ...
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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? ...
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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 ...
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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 ...
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70 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 ...
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1answer
55 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.
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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 ...
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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 ...
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38 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?
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31 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 ...
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1answer
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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 ...
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4answers
181 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 ...
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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 ...