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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is photon direction affected by source velocity?

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
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1answer
48 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 ...
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1answer
47 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 ...
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1answer
59 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 ...
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1answer
80 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 ...
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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 ...
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0answers
22 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 ...
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1answer
71 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 ...
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1answer
40 views

Absorption of photon as particle by an electron

As the photon gets absorbed by the electron and goes to higher energy state, does the photon remains in the electron itself in some form (radiation energy), thereby increasing the mass of electron?
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1answer
43 views

Why does quantum mechanics produce different predictions for Bell test experiments than classical mechanics?

I understand that experimental results from Bell test experiments have shown that measured correlation is a cosine function of the angle between the detectors. What I am struggling to grasp is why ...
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3answers
273 views

Why isn't a Photon justified in concluding that it is at rest and everything else is moving past it at c? [duplicate]

Why isn't a photon moving at c not justified in concluding that it is at rest and everything else is moving past it at c since relativity postulates that the laws of physics are invariant (i.e. ...
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0answers
16 views

Show that an isolated photon cannot undergo pair production [duplicate]

I need to see the mathematical details as how the conservation of four momentum is violated.
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2answers
38 views

When i look to a lamp at night, from a distance what happens?

Lets say its night, and i look at a lamp 20 meters away from me. Im obviously in the darkness, but i can see the light from the lamp, if the photons need to stimulate my eyes in order for me to see, ...
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1answer
122 views

Is there any observational test that could be done to approve\ disapprove the Tired Light theory? [closed]

Tired light is alternative explanation for the redshift-distance relationship and for the metric expansion of space. The suggestion is if photons lost energy over time through collisions with other ...
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1answer
18 views

Why does Diffracted Light cone diameter change in relation to angle of light beam?

I have a question about light diffraction. Take a look at these images of the Pantheon oculus. Now what I don't understand, in the first picture, the light is coming in from overhead and forms a ...
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1answer
30 views

how much energy efficiency is there when photons converted to positrons? [closed]

actually i am participating in NASA ames space settlement and want to transmit electricity through antimatter. i had created the photon by using the carbon dioxide, nitrogen, helium and hydrogen. i am ...
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1answer
49 views

How to calculate a straight edge diffraction pattern

A straight edge diffraction pattern is not the same as a slit or multiple slit diffraction pattern. The spacing between fringes is not equal but gradually gets smaller the farther out you go as in the ...
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3answers
49 views

Does unpolarized light means that photon is in superposition state?

I read that a polaroid filter is made of many long chain of molecules aligned in one direction and will only allow the vibration of light with the same alignment as the filter to be absorbed. I ...
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1answer
33 views

Showing the annihilation of an electron-positron pair [duplicate]

How to show that the annihilation of an electron-positron pair under emission of one real photon (mass zero) is forbidden by energy-momentum conservation, the emission of two photons is allowed?
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0answers
50 views

Photon has energy but no mass [duplicate]

The photons energy is defined as Plancks contant multiplied by the frequency of the light wawe it represents. However Einstein states that the total energy of a particle with rest mass m is m times c ...
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0answers
36 views

Help in writing down Feynman rule? [duplicate]

I have a term in my Lagrangian that looks like: $A^\mu B^{*\nu} \partial_\mu B_\nu - A^\nu B^{* \mu} \partial_\mu B_\nu$ where A is the photon field, and B is a charged, massive spin-1 boson. I am ...
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1answer
7 views

Maximum energy transfer in Compton process

Consider a gamma ray incident on an electron at rest with wavelength $\lambda$, in a Compton scattering process . What is the maximumc kinetic energy the electron can gain from this? Can the gamma ray ...
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1answer
52 views

Was decoupling actually detripling?

As I previously understood it, before recombination, high energy photons were bound up in interactions with excited electrons, meaning electrons couldn't settle into orbit with protons and other ...
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1answer
74 views

Mathematical proof of an electron cant absorb a photon [duplicate]

How can we mathematically prove that a free electron cant absorb a photon totally?
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6answers
84 views

Does wavelength of photons depend on the medium?

I have read that photons always travel at the speed of light.So if I have a bunch of photons travelling in air then they will have an energy given be E=hf ;where f is the frequency. Now if I place a ...
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0answers
7 views

type of photoluminescence depending on the FWHM

Depending on the FWHM of CdSe quantum dots, is it possible to estimate the type of dominant photoluminescence in question, as in excitonic luminescence is supposed to have a narrower spread than ...
6
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1answer
588 views

How is a CCD able to collect images in drastically different lighting conditions?

I have read the basics of how a digital camera works. As much as I have understood, the digital cameras have a device called a CCD on which photons coming from the lens are incident. The CCD then ...
6
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1answer
110 views

Transformation of photons under Lorentz transformation

This question is a continuation of one of my earlier post. In this post,I asked about the transformation of photon fields under rotation. Here I generalize the question to Lorentz transformation, and ...
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1answer
42 views

What happens if two possible paths interfere with each other but are different in their length?

Can you explain what happens if two possible photon paths interfere with each other but are different in their length? When does the interference pattern appear? I suggest it happens after the time ...
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1answer
52 views

What is the group transformation property of photons under rotation?

Both the photon and the W boson are spin-1 particles. Under rotation W boson must transform under the 3-dimensional representation of SU(2). However, the photon has two degrees of freedom (or helicity ...
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0answers
10 views

Do we know how much energy is released in internal conversion (fluorescence)?

In the Jablonski Diagram, when photons hit a surface and certain frequencies are absorbed, then internal conversion occurs to the excited portions of the surface and energy is released as heat (If I ...
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0answers
61 views

Does this vertex equal 0?

If I have an interaction term in my Lagrangian that looks like: $\mathcal{L}_{int} = (\partial_\mu B_\nu)(A^\mu B^\nu - A^\nu B^\mu)$ where B is a massive spin-1 field. Am I correct in thinking that ...
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2answers
49 views

If 2 photons never interact with one another, how come we get an interference pattern? [closed]

OK better to be insured: I'll exclude very high energy photons. Albert Einstein's paper on photo electric effect say that light is quantized loosely speaking, now in a double slit experiment How can ...
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1answer
70 views

What happens to photons, electrons, etc [duplicate]

What happens to photons when they hit our eye? where do they end up? if they generate heat, why our eye don't get overheated? Similarly what happens to electrons when the light hits certain metals, ...
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1answer
36 views

Good book on quantum photonics and applications

I am just looking for an easy to read introduction to quantum photonics and possible applications. Terms like "Fock state" and "Photon (anti)bunching" should be understood after reading. Perhaps also ...
3
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2answers
115 views

Redshift due to a static gravitational field and the conservation of energy [duplicate]

I am standing on the surface of some planet. Gravity is described via General Relativity with some static metric (e.g. the Schwarzschild metric, so static means no time dependence, but the metric may ...
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0answers
41 views

Photon gas into a Black hole

Can a photon gas have so much energy that it collapse into a black hole just like a regular star?
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1answer
35 views

How often does photons morph into matter and antimatter?

We know that matter-antimatter collisions are reducing the two into pure energy or photons. Similarly the reverse is possible where a photon can spontaneously morph into two equal particles of matter ...
3
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1answer
100 views

Is it experimentally proven that photons travel at speed $c$ in vacuum?

Are there experiments which show that single photons (not classical em waves) travel exactly at $c$ in vacuum? What is the error bar in that case? The question is posed due to the fact that loop ...
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2answers
121 views

Red Photon Blue Photon

Why in space red light travels farther and is more observed in dying stars before a star becomes a black hole? while on Earth in water and air the blue light travels the farthest. For example: a ...
2
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1answer
153 views

Slow light that does not go back to it's original speed in vacuum [closed]

I have watched today episode of scishow where Hank claims that photons can be permanently slowed down to speed that is less than speed of light. ...
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1answer
56 views

Gravitational Lensing Diffrence between Big and Small Black Holes

Would you see more of the back holes iris in smaller black holes compared to larger ones and if so can one be big enough the photon sphere would completely cover it and it would look like distorted ...
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0answers
30 views

Can you grow more Biomass in a brickhouse only powered by solar cells than in a greenhouse? Will we ever be able to? [closed]

Right now I read that 1m² of solar cells generates roughly 100Watts of energy. There are really efficient Grow LEDs that use only two spikes in the lightspectrum to make plants grow. I have seen some ...
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1answer
45 views

So why are photoelectric panels flat? (Part II)

In this post So why are photoelectric panels flat?, I've asked if we could use flat photoelectric panels with hemispheric cells. Most of the answers seemed to say it would not work. Anyway, I'm ...
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0answers
52 views

What's the analogy of a single photon from the perspective of “classical electromagnetic wave”?

I guess there isn't an accurate analogy. But what is the best analogy we can use? It seems an idea sinusoidal wave of a single frequency doesn't fit as a photon at all. In a certain sense, at least ...
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4answers
1k views

So why are photoelectric panels flat?

In this post Why not use our own light production to produce new energy instead of wasting it?, I naively asked if it was possible to also recycle our own lightning at night. someone, in his answer, ...
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0answers
15 views

Stark broadening and Voigt fitting

I have LIBS spectral data acquired with a CT spectrometer of resolution 0.4nm. I fitted the Voigt profile into the spectral peak at $\lambda_0$. The lorentz $\Delta \lambda_L$ and the gaussian ...
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8answers
449 views

Why not use our own light production to produce new energy instead of wasting it?

Why don't we use our own light production at night (I mean home, buildings, streets,..., lighting) to charge photovoltaic panels instead of wasting it?
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2answers
99 views

Electron-positron annihilation [duplicate]

Photon pair production in electron-positron annihilation is necessary to conserve the linear momentum. In such discussions the electron-positron pair collide with equal and opposite momentum, if they ...
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1answer
49 views

Effects of gravity on light on the surface of the Earth [closed]

I read over the question and answers on the effects of gravity on light. I would like to ask a more specific question about gravity and light. What is the effect of gravity on light on the surface ...