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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How do solar panels generate infinite electricity?

We know that solar cells generate electricity utilizing the energy of the photon, but how can they generate electricity forever? In a n-type terminal we have the bond of silicon and phosphorous so ...
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Selection rule $\Delta S=0$: Why does a photon not interact with an electrons spin?

When talking about selection rules in atomic physics, many books state that the photon interacts with the electrons angular momentum such that that $\Delta l=\pm 1$. Absorbed/emitted photons exchange ...
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Do photons emitted from a LED show bunching?

If photons are emitted from a thermal source, we get photon bunching. For coherent radiation, the detection probability doesn't change after detecting a photon. For single photon sources, we get ...
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65 views

Probability of photon emission

If a photon of a given wavelength is absorbed by an electron (for simplicity, let's assume the electron has only one excited state), does the probability that the electron jumps to its excited state ...
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115 views

Is a single photon also a Maxwellian wave?

A photon is associated with the equations $h\nu$ and $\frac{hc}{\lambda}$. My book (Serway Modern Physics) says that Einstein explained the photoelectric effect by assuming that the classical ...
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Why would the curvature in space-time attract photons which have zero mass? [closed]

I know that we are surrounded by dark matter, does the dark matter affects space time ???and I know the reason for gravity according to explanations in general relativity. But all the explanation ...
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Do solar panels work forever?

Do solar panels generate electricity infinitely? IF YES then how do the electrons in the n-type which go to p-type then how do those electrons restore themselves. I mean in n-type terminal we have the ...
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30 views

Photoelectric effect and variation of current?

Say a photon of frequency $\nu_1$ strikes the metal, and we have certain kinetic energy which is stopped by $V_{stop1}$. Now for frequency $\nu_2$ for same metal it will have $V_{stop2}$. Now ...
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Energy-level choice for electron at photon emission [duplicate]

An electron absorb a photon and jumps to the last energy level.Now when it goes done,How does it choose which level it will step down to?.Also I've come to now that it can omit one step(e.g from 5th ...
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Moving objects using light

Photon do not have mass but they have momentum, can we use laser to pick up golf ball and hurl it several yards away without burning it into crisp?
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Photoelectric effect and work function relation

Let's consider the graph above for two metals $M_1$ and $M_2$ showing relation between photocurrent and potential. First question that I want to ask here is that how do you relate stopping ...
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114 views

Why can't light escape a blackhole? [duplicate]

Gravity attracts objects which have mass right. We know that light is massless so why does a black hole's gravity attract light?
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How does light oscillate?

Why do we say that electromagnetic wave is oscillating? Or does light propagate really in a wavy form like this image? What is making the photons oscillate and how is it oscillating is it ...
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Why doesn't light affect a compass?

In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
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Does a photon travel in all directions?

For example i am standing and a beam of light is passing in front of me. I am able to see that beam of light so does it mean that photons are travelling in all directions other than the photons which ...
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4answers
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In $1$-dimensional space, how would the gravity generated by an electron affect a photon moving away from the electron if the photon can’t slow down?

Suppose we had a universe obeying the same physical laws as our own. But it had only one spatial dimension (represented by the $x$ axis) and it was totally empty. There are just two point-like ...
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Optics - Photodiodes - minimum photon energy that a photodiode will be sensitive to [closed]

I'm foraying into the world of photodiodes, and I'm trying to calculate the minimum photon energy required for the photodiode to be sensitive to. Symbolic expressions desired. Minimum detectable ...
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How does the photon differentiate between events?

As far as I know for a photon that's moving at the speed of light (obviously) time comes to a halt and space contracts to a point, making all travels instant from its perspective. Now this is the part ...
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In an electron-positron annihilation, in what direction are the photons released?

I read that, in an electron-positron annihilation, at least 2 photons are produced, because of the law of conservation of momentum. my question is: in what direction are those photons released? and ...
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3answers
334 views

Do photons lose energy due to gravitational redshift? If so, where does the lost energy go? [duplicate]

In the gravitational redshift, the frequency of photons radiated from some source is reduced. As the energy of a photon is given by $\hbar\omega$, if the frequency is reduced where is the lost energy? ...
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Photon propagator inverse

If i have the operator $D^{\mu\nu}=\partial^{\mu}\partial^{\nu}+m\epsilon^{\mu\alpha\nu}\partial_{\alpha}$. What's your inverse $(D^{\mu\nu})^{-1}$?
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Photons under pressure

Does it make sense for photons to be put under pressure, if so how would this be measured? I'm wondering because I would like to plug in $E = h\nu$ into the formula for enthalpy.
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How to count the number of modes/polarizations of a Gaussian field theory?

A Gaussian (free) field theory is described by a quadratic action of the field, e.g. $S=\int\psi^\dagger K\psi$ (or $S=\frac{1}{2}\int\phi^\intercal K\phi$ for real fields). Usually one just need to ...
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Does a superconducting coil need a minimum amount of electric current to be a superconducting magnet?

I'm not about that for a tiny amount of Cooper electrons perhaps we can't measure the magnetic field. I suppose that it needs some influental electric current below which the coil isn't a superfluid ...
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photon wave function, double slit, single photon source

There's an old argument by Newton and Wigner, that the photon as a massless particle can't have a position operator and therefore no position space wave function. How does this tie in with the double ...
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3answers
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How does an Inductor “store” energy?

It seems to me that an electromagnetic field is nothing more than a collection of photons, which as I've heard, extends through space infinitely. Why is it, then, that an inductor such as simple ...
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Models of light

As far as I'm aware, there are two different (and almost contradictory) models that describe the behavior of light: light as a wave (EM), and light as a particle (QM). From what I've heard, depending ...
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Does photon polarization take place without scattering processes?

Behind two perpendicular crossed polarisation filters (for visible light) the intensity of light will be zero. After installing a third filter between the two others non parallel to each of them some ...
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Quantum mechanics between proton & electron but not electron and positron

An electron approaching a proton gives off the hydrogen spectra. An electron approaching a positron does not give off the spectrum of hydrogen. Why? Both scenarios are -1 charge approach a +1 charge. ...
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Can I use the grand canonical ensemble for a photon gas?

I have been reading about photon gases at https://www2.chem.utah.edu/steele/doc/chem7040/chandlerch4.pdf. They do the analysis using a canonical ensemble. Since photon numbers are not conserved, I ...
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Why most of physics is somehow related to light? [closed]

It seems that for the past 200 years, every physicist is concerned about light. For example : Newton's particle model, Young experiment, Photo-Electrict effect and Einstein's formula, Special ...
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Is Maxwell's field the wave function of the photon?

In his ArXiv paper What is Quantum Field Theory, and What Did We Think It Is? Weinberg states on page 2: In fact, it was quite soon after the Born–Heisenberg–Jordan paper of 1926 that the idea ...
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260 views

Is Magnetic Field is made of Photon? Is there any frequency of Magnetic Field waves? [duplicate]

(Considering the What is a magnetic field question which is asked on just 8th march, by @DragonSlayer3 and my own question which is left with negative points and closed, Photon Energies in sunlight, ...
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Why photon propagator has metric tensor additionally?

Klein Gordon propagator is (Peskin p-30) $$ D_F(x-y)=\frac{i}{p^2-m^2} $$ which is actually Green function of KG field. But photon has $g_{\mu\nu}$ additionally in the numerator. I would expect its' ...
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X-ray radiation - What does h * fmax = e * U mean?

I'm trying to figure out this formula for X-ray radiation $$h \times f_{max} = e \times U$$ $h$ = Planck's constant $f_{max}$ = maximum frequency, in hertz (?), that the photons can have because ...
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Dose-depth curve of photons vs. protons

The dose-depth curve of protons and photons can be seen in the image below: Now, what I've heard is, that in some cases, proton therapy is advantageous compared to photons, and of course the other ...
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3answers
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Is it possible to create a beam of light with frequency of 0?

Is it possible to create a beam of light with frequency of 0? So this would involve photon(s) that move forward without fluctuating with any frequency. If yes, how could this be done? Also, ...
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Saturation point of incident Light on an object

Since the color of objects depends on the parts of the visible spectrum reflected out and the remaining is absorbed; is there any maximum limit to which the absorption can take place? In other words, ...
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Does each photon have a unique wavelength?

Since the frequencies (or inversely, wavelengths) of photons are part of a continuous realm, doesn't this mean that no photon has exactly the same frequency? Two photons might have the same apparent ...
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Do photons exert gravity? [duplicate]

I read about GR today and came across the Bonnor beam. As I understand it, two parallel light beams (in a flat space) will in fact creep – slowly – towards each other. As Wikipedia puts it: On the ...
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Do photons have a spectrum like light when they are treated as waves?

If light can be treated as both a particle and a wave, are there things called infrared photons, or ultraviolet photons etc, as there are infrared waves, or ultraviolet waves? Or are photons just ...
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Where do photons go when they are absorbed?

The answer I usually get (and I'm paraphrasing here) is that they disappear and are instead absorbed as heat energy. But I find it hard to believe that the photon simply "disappears." Common sense ...
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Spectral lines and QM

In the various presentations I've seen so far in atomic physics of series such as the Balmer series, the wavelength of each spectral line is definite - but in QM, free particles have no definite ...
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Can we change a photon's frequency in mid-air?

Can we have a light source emitting photons in the infrared range and after, lets say, 5 meters, these photons become a photon in the x-ray range? The only way I know we can change a photon's ...
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2answers
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Do light particle/waves have a frequency? [duplicate]

I sought the answer to the question about amplitude of light waves first, but I was actually thinking about whether the wavelength is the only property of a single quanta of light. I suppose direction ...
1
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1answer
52 views

Can an electron which is a bound in an atom absorb more than one photon at the same time? [duplicate]

Can an electron which is a bound in an atom absorb more than one photon at the same time ? In specific during photo-electric emission can an electron take in more than one photon if one photon doesn't ...
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What happens to photons that get trapped in a black holes event horizon?

So, I know that photons do not travel fast enough to escape a black hole once it passes the event horizon. Also, I know that the photons themselves aren't affected by the gravity, but rather their ...
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If photon-photon interactions are impossible, how are higher harmonics generated?

In nonlinear optics, it is a rather common process to use nonlinear materials to produce higher harmonics of an incident wave. About the mechanism of the generation of such higher harmonics, it is ...
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Entangled Photon (laser pointer)

From a laser pointer emission; is it creating entangled pairs of photon? is it possible to get more than "pair" entangled, like group of photons all entangled?
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Is this fine to think of light as the following? [closed]

Is light quantums (increments [photons]) of the electromagnetic waves which are synchronized by oscillations of electromagnetic fields