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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Will objects become invisible at relativistic speeds?

Let us assume there is a mirror travelling at extremely relativistic speeds, perhaps few picometers away from speed of light, and let us assume we have a very thin detector which is very small perhaps ...
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5answers
692 views

What happens when two photons collide with one another, head on, dead center? [duplicate]

If two photons were to collide directly, head on, and are of the same energy, what happens? Are new particles created, is energy released? Or do they just pass through one another?
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1answer
429 views

Can two colliding photons create a Higgs Boson?

The LHC discovered the Higgs using the following decay mode: $$ H^0 \rightarrow \gamma \gamma $$ This got me thinking: if we reverse this mode, will it be valid? In some annihilation/decay pairs, ...
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Why does time stand still for light? [duplicate]

The source for this is the book "Einstein for Dummies", page 330, chapter 10.
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2answers
46 views

Does light ever experiences acceleration? [duplicate]

Till now I have learned that light has fastest speed. But I have also noticed that wherever it travels it only experiences retardation. So I wanted to know if light ever felt acceleration naturally in ...
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1answer
23 views

Recreating an image from a photometer or similar light-detecting device?

I'm thinking if it is possible to recreate an image from data from this kind of device. It is known analog signals theoretically have infinite resolution, but since we use them in discrete systems ...
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2answers
101 views

Why are electrons alike but photons not?

Perhaps this is a misconception, but why are electrons alike and photons not? Given two photons, they may differ by having different frequencies (energies). Given two electrons, there are just two ...
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0answers
37 views

Can pair production be used to explain the EM Drive? [closed]

My understanding of the EM Drive: LOTS of energy and a little light is input into the system. A tiny amount of force is then exerted out of the system. Can this system be explained simply through ...
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7answers
8k views

Why can't we see light travelling from point A to B?

Let's say we have a cloud of dust which is a lightyear across and someone shoots a beam of light from point A to B , why it is not possible for an observer far far away to see the light while it ...
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2answers
71 views

Quantum electron and field interactions

What is the proper way to consider the electric field generated by an electron wavefunction governed by the Schrodinger equation? Can you get a result that would match observation, or is this a ...
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2answers
85 views

Magnetism and Photons

Knowing that magnetic field is made from photons. Where does a magnet gets it's photons from to create a magnetic field. Are the photons created within the magnet, or does the magnet capture photons ...
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1answer
48 views

Light changes wavelength in the presence of gravity, can the quantum theory of gravity explain this?

If light changes wavelength in the presence of a gravitational field, how can this be described by the quantum theory of gravity?
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2answers
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will osmium or lead stop all high-energy photons in a shorter distance?

I remember seeing a similar question to this one on Physics StackExchange once. Most of the answers were to the effect of "I don't like the way this question is phrased, so I will insult your ...
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1answer
57 views

Can a photon excite an electron via the uncertainty principle?

An electron is trapped in an infinite well potential with a width of $\Delta x$. A photon of wavelength $\lambda $ < $\Delta x$ is fired at the electron and misses or rather they don't interact. ...
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1answer
66 views

How are photons effected by gravity? [duplicate]

If we use E²=m²c⁴+p²c², and we know mass of photon is zero, and they have momentum but why aren't they affected by gravity.
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0answers
30 views

Can we see the photon sphere from outside? [duplicate]

This question came to my mind when i saw the movie interstellar. In the movie there is a scene with a black hole and a sphere of light around it, what i assume to be the photon sphere. You can see it ...
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36 views

The movement with the speed of light [duplicate]

Light moves at $3\times 10^8$ m/s, but is this speed always so?, imagine if I am in a dark room that is $1$ light year long and I am standing at one extreme end of the room, and there is a powerful ...
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2answers
54 views

How does a Black hole attract light? [duplicate]

Please no hate for lack of knowledge: I am somewhat fascinated with the subject of black holes. However, I do not understand a concept which is constantly attributed with black holes: that a black ...
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0answers
28 views

Photon's behavior from 1-dimensional realm to 3-dimensional realm

I know that photon's behavior can be fully analyzed (or at least a solid theoretical explanation is present, see molecular QED book) when the photon is emitted and absorbed by same dimensional ...
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2answers
135 views

If photons don't “experience” time, how do they account for their gradual change in wavelength?

It is often said that photons do not experience time. From what I've read, this is because that when travelling at the speed of light, space is contracted to infinity, so while there is no time to ...
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53 views

Size and energy of a photon

I would like to ask the opinion of some expert regarding the concept of the egergy and size of a photon in correlation with the redshift effect. I have seen very complex demostration trying to explain ...
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1answer
86 views

Can I catch a single photon with webcam's CMOS or CCD sensors?

I thought it would be nice to capturing single photons using a webcam's sensor due to simplicity. I've read that ccd and cmos sensors have a certain percent of quantum efficiency. What about ...
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0answers
25 views

Break time-reversal symmetry in photonic system without using bias magnetic field

In photonic system, e.g, photonic crystals, people usually use ferromagnetic material or so called Tellegen medium which acts as effective field bias to break the time-reversal symmetry. I just want ...
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1answer
103 views

Is the wobbly rope depiction of a radio wave inherently wrong? And how do vectors of parallel waves align with each other?

I don't have a scientific education, yet I'm scientifically curious. Among other things, I'm struggling to understand the nature of electromagnetic waves. What I have recently realized is that the ...
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1answer
57 views

How is light slowing down in a medium thought of in the photon picture? [duplicate]

The speed of light in any medium besides vacuum is smaller than $c$. In a classical way, I just look at that as a wave that propagates less fast, the change in EM-field is passed on slower. How should ...
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1answer
50 views

Gravitational “acceleration” and frequency change of a photon?

For massive particles, force translates into acceleration which again is a change of the velocity vector in direction and/or magnitude. For a photon, the velocity magnitude cannot change, only the ...
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1answer
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Is the Energy of an absorbed photon exactly the energy of the band gap?

I was wondering, if the Energy of a Photon which is absorbed by an Electron, hast to be exactly the Energy of the bound gap. So if i have two energy levels in an atom $E_2$ and $E_1$, does my ...
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1answer
92 views

How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model

I understand longitudinal waves. For example, I've got a clear mental modal of air waves: a slice of air becomes overcompressed, then the slice next to it becomes overcompressed and the first slice ...
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0answers
27 views

Does the entropy of the universe change as expansion exceeds the speed of light?

The potential encoded information in a photon that is at the edge of the observable universe would seem to be lost as the universe expands. Does that loss of information contribute to the overall ...
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1answer
50 views

What could cause a diode laser to be emitting the half-harmonic of the fundamental frequency?

I have a 405nm laser which is seemingly outputting a small portion of 810nm light. I am wondering what mechanism this could be caused by. Is this a down-conversion phenomenon or perhaps just another ...
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4answers
114 views

Can a photon have little to no energy and/or speed?

Can a photon move more slowly than the speed of light and behave 'non-relativistically,' so to speak. Perhaps another way to express my thought is: could we stop a photon from moving?
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1answer
46 views

Brightness of light sources

I would like to know what determines the brightness of light.I'm confused,After hours of reading i got these definitions mixed up i need to link them together : Light intensity Brightness of light ...
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1answer
49 views

Why doesn't light vibrate in-situ?

Light always moves in a straight geodesic path (shortest distance between 2 points in flat space where gravity is homogeneous) across 3 dimensions of space and 1 dimension of time. It is consists of a ...
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0answers
38 views

Photon Energy and Einstein Equation $E=mc^2$ [duplicate]

If the mass of a photon is zero and these ones travel to the light speed, how may I explain Einstein's equation $E=mc^2$? It is well known that the energy associated to a photon may be calculated ...
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1answer
87 views

What happens to theoretical physics if a photon has non-zero mass?

I want to know the theoretical implication if photons have a non-zero mass. What happens to the Maxwell equations? What happens to QFT? If the photon have mass it can decade?
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1answer
62 views

How can we see objects that are so far away? [duplicate]

The HUDF used to be the deepest image of the universe ever taken by the Hubble telescope, the furthest star in this image is 59000 light years away. The star in question: Now Imagine a light ...
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1answer
26 views

During transition of the electron from high to low energy state, is the photon released always of same energy?

Is it not possible that during transition of an electron from higher to lower energy state, it can release multiple photons of low energy instead of a single photon of the exact energy difference ...
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2answers
334 views

Why are non-linear optics called non-linear?

Looking at the wikipedia article on nonlinear optics you can see a huge list of frequency mixing (or multi-photon) processes. What makes these different from single-photon interactions? More ...
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1answer
80 views

How do solar cells increase the lifespan of the Sun?

While reading "Physics of Solar Cells" by Würfel, I came across an amusing statement: An interesting aspect arises if we had to pay for solar energy, but could also get a refund for energy ...
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36 views

Don't photons pass photons move away at speeds faster than light? [duplicate]

I understand there is a longstanding rule that nothing travels faster than the speed of light... but if you had two flashlight aimed at each other and turned them on inside a vacuum the photons from ...
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1answer
67 views

How is polarization vector in QFT related to polarization in classical electrodynamics?

As i know in classical electrodynamics polarization shows the orientation of the electric vector in a plane perpendicular to the direction of propagation of light. But in quantum field theory ...
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1answer
28 views

Quantization of energy of phonons

when taking into account of energy of photons, the relationship $E=nh\nu$ stands because it is said that the Energy is proportional to the frequency of the electromagnetic wave, however when the ...
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28 views

What forms does the energy of a photon get converted to after absorption

Assume an object which has a high absorption rate of light. Now my question is, if you shine light on the object, what all forms of energy does the object acquire? I know there will be an increase in ...
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1answer
74 views

Why are photons bosonic?

I am studying the quantization of the electromagnetic field. My text quantizes by changing amplitudes to ladder operators, by putting in an action and by imposing bosonic commutation relations upon ...
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4answers
88 views

Photon Emission/Absorbsion from the Photons Perspective [duplicate]

First some assumptions. 1) Photons travel at the speed of light. 2) From the photon's reference spacetime is contracted to 0 length in the direction of photon travel. 3) From the photon's reference ...
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2answers
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Spin zero photons

As I understand it, the reason why there is no Spin 0 Photon is because the polarisation of an EM field lives in two dimension. Hence we only have two basis vectors, yielding two pairs of ladder ...
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2answers
105 views

Why is a photon its own anti-photon?

Two properties of a photon that I have considered in trying to answer this myself : Photons are electrically neutral, so there is no need for "anti-photons" to preserve conservation of charge. Take ...
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22 views

Compton effect confusion

In a certain question we were told that a photon collided with an isolated electron and as a result its wavelength changed. We were told to calculate the initial and final momenta of the photon which ...
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1answer
26 views

Reflection of light at a microscopic level [duplicate]

I always read that light is reflected by a mirror! My question is how does reflection takes place at microscopic level? Mirror is just atoms and electrons are revolving around the nucleus ! So where ...
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1answer
69 views

Are there any naturally occurring examples of photons without mass?

I read that a photon is said to have zero mass at zero velocity. Does this mean that they only exist in a state of probability until observed && interacting with some system? And then when ...