Questions tagged [photons]

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 interactions.

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72 views

Why can't two truly identical experiments on quantum scale give the same result?

When we refract light on air/water interface, some part of light is reflected while some of it gets refracted. My question is when we consider light as a photon and send it (photons) one by one, what ...
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How do you “store” a photon?

This article discusses the recent invention of a "quantum radar" that works by bouncing one photon off of something, storing a photon that's entangled with it, and watching for interference on the ...
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Comparing quantum and natural Hamiltonian dynamical systems for the hydrogen atom: Why is quantum preferred? [on hold]

The quantum model for the hydrogen atom is a Hamiltonian dynamical system based on Schrödinger operator $H$. When compared with the physical atom it has important shortcomings. First and foremost the ...
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Glow in the dark fading

I am doing some experiments with "glow in the dark stars". from basic theory I expected the light to drop off at:- $$I = I_0 e^{-t/T}$$ However, on measuring this with a Lux sensor I find the drop ...
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Photon size vs. Planck length [duplicate]

Another attempt to pose a correct question: with what probability, i.e. a real number in $[0,1]$ photon hits a sphere with diameter the size of Planck length?
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How do materials absorb light

I'm curious how light is absorbed in materials. From what I understand, when an electron absorbs a photon, it gets excited to an energy level that is higher than the level it's in and the energy ...
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29 views

Energy threshold for photon

I just read https://en.wikipedia.org/wiki/Annihilation#Examples and there is the popular $ e^+e^- \to \gamma \gamma $ reaction described. Is it always possible to produce a $ \gamma $? A photon does ...
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Greatest relativistc mass possible for a single photon

I have been told that photons can not be blue shifted to the point where they become black holes, although a photon with a Planck scale wavelength would also have a relativistic mass equal to a black ...
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Sequential Double Double Slit Experiment?

Let's say you arrange the double slit experiment so that there are two sets of two slits one after the other. Like so: ...
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How can light reach its speed? [duplicate]

The mass of a photon is said to be 0, But light (photons) get attracted due to gravity of a black hole, that means photons have a mass which is very very very small. And we know that any object with ...
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What is the mass of photon? [duplicate]

I'm sorry if this question is asked before, but I searched through the site and none satisfied me. In most of the books I've come across, they just write "rest mass of photon is zero." But never talk ...
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What are the ways we have control over single photon emitters? Are there single photon emitters “on demand?”

I am wondering what are some of the ways we have been able to get more control over single photon emitters. What advances in technology have we made over the past years? Is there anything that ...
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Why are there two photons in pair production Feynman diagram? [duplicate]

Given I wonder why are there two photons entering in a) pair production? Isn't it one photon resulting in $e^+e^-$ ?
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Are photons emitted by a magnet?

If you put a photon detector near a magnet (with the magnetic field static in time), is there some probability that the photon detector will detect a photon? Does QFT not predict that a photon could ...
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Are the electrons' orbitals the same for all atoms?

Are the electronic orbitals of an atom always quantified in the same way (i.e. the same energy required to reach the next level), or does each atom have its own values for each level? If the ...
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Compton effect in dependency on the atom number

I can't find information about the influence of the atom number on the compton effect. Often I read that the cross section is proportional to the atomic number but I also read that materials with a ...
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When two photons annihilate each other through destructive interference, where does the energy go? [duplicate]

When two photons annihilate each other through destructive interference, where does the energy go? Perhaps this is only answered by ‘wave type’ questions and answers? Does the conservation of energy ...
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What is Rabi splitting? Is it related to Autler-Townes splitting?

A quantum optics text I am reading claims that the proper way to analyze a two-level atom's interaction with light is to, conceptually speaking, consider four states: $|g, n\rangle, |e, n\rangle, |g, ...
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Reason behind inner shell excitation phenomenon [closed]

Is there any simple explanation of inner-shell phenomenon. I wanted to know that why photons with high energy do not excite outer shell electrons.
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Photon-Electron interaction (Compton and Photoelectric effect)

(Some context : I am a first year engineering student and i have conceptual doubts in Compton and photoelectric effect. I have read a book "Concepts of modern physics"-Arthur Beiser and talked to my ...
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How do I calculate the relative number of photons per wavelength emmited by the sun?

Assume I generate $n$ photons emmited by the sun. They have wavelengths between 390 and 750 nanometers. How do I find out the number of photons that correspond to each wavelength: How many of my $n$ ...
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Can we affect the size of the universe with the observation of light?

Adding on to THIS question I would like to take this question a bit further, and forgive my ignorance of the details as I have never taken any formal training on such subjects. But it's said that ...
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Can monochromatic half wavelenght wide beam of photons be incoherent?

Imagine horn antenna that leads to waveguide which is half wavelenght thick. Incoherent monochromatic light source is placed in front of the horn antenna. My question is this, will the antenna and ...
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What is the most efficient single-photon detector to date?

(This question depends on the current time period, so the reader should make note and be aware of the date of the posted answers.) I am wondering what is the most efficient state-of-the-art single-...
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Photon-Atom Collisions

I know that when a photon collides with a stationary H- atom, an elastic or an inelastic collision takes place depending on the energy of the photon. Do photons and atoms obey the classical laws of ...
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Entanglement Observation

I'm thinking that light slows down in a medium because photons are being absorbed and then remitted by atoms or molecules in the beam. This would imply that the photons which leave a lens or filter ...
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Shouldn't the remaining photon energy be transferred to both electron and ion in a photoionisation?

I'm studying photoionisation and photodissociation, and I'm having a hard time trying know the microscopic details of such processes. I've read that in a photoionisation the photon is absorbed by a ...
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Particle nature of radiation [duplicate]

If quantum of radation concept is used to define particle nature of radiation, then why it has a frequency?(E=hv)
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The “different Hilbert spaces” of a photon?

What I understand of Fock states so far: They describe the quantum state of a bunch of photons. A single photon can be in several different energy states, and when these photons are tensored together -...
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Light photon wavelength not equal? [closed]

Added reference points from photo from this article: https://cosmosmagazine.com/physics/what-shape-is-a-photon As you can see in the reference photo the order of intensity is highest at point A (...
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High speed and low speed photons (hypothesis - difference/relation)

In this question I found an interesting answer with the source. Quotation: A telescope viewing a supernova from over 16 billion light years away recently clocked the low energy photon arriving 5-...
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How is the optical conductivity for a single photon related to normal conductivity?

Planck argued that light energy is carried by photons. The electric optical conductivity for an electromagnetic wave is classically derived. How does this conductivity look like for single photons?
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Photoelectric effect photon attenuation disctontinuities

Can anyone explain why there are the discontinuities in proximity of the electron energies? I was thinking : every time the photon gains enough energy to ionize a new and a more bounded electron there ...
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Why are 2 gamma photons created? [duplicate]

When a positron and an electron come together they annihilate and produce 2 gamma photons $$e^+ +e^- \rightarrow 2\gamma$$ I can understand that they must be produced in pairs to conserve momentum. ...
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How can light be made up of particles?

In order to explain photoelectric effect, Einstein suggested that light is made up of photons, but I don't understand how could this have made sense when you know that light is an electromagnetic ...
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Does space expansion affect the CMB photon frequency?

I have read this question: Effect of expansion of space on CMB where Ted Bunn says: For definiteness, let's consider a wave packet of electromagnetic radiation with some fairly well-defined ...
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Can GWs move objects (excerpt pressure on matter) like EM waves?

Gravitational waves are real, they have been observed. Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from ...
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What do these momenta mean? [duplicate]

I'm studying the motion of photons near a Schwarzschild black hole. My coordinates to describe the position of a photon are $~r$, $~\theta$, $~\phi$ and $~\textrm{p}_\textrm{r}$, $~\textrm{p}_\...
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Classical wave energy vs Photon energy

The classical theory says that the intensity of light is proportional to the square of the amplitude of an oscillating electric field. Quantum theory gives the intensity of light as proportional to ...
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1answer
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How to define the proper time of a photon?

I'm writing a paper about the motion of photons near a Schwarzschild black hole. At some point there's a derivative of the Hamiltonian of the system with respect to time $\tau$. I need to explain what ...
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How does a heated object lose thermal energy in a perfect vacuum?

Suppose I heat up an arbitrary object to an arbitrary temp and then place it in a near perfect vacuum (let’s assume inter-galactic space). If there is essentially nothing for the object to transfer ...
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Would the results of the Double Slit Quantum Eraser be the same using massive particles?

I'm wondering if the double slit quantum eraser experiment would produce (or does produce, if it's already been done) the same results if massive particles were used instead of photons. My reason ...
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Due to the probabilistic nature of particles, is it possible for a photon to arrive at a location slightly earlier than the speed of light?

Due to particles not having a specific location in space unless it is observed (i.e. it is a probability wave), would this mean that a photon can appear slightly ahead of where the speed of light ...
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Four-momentum of a photon emitted from an accretion disk

Consider a non-rotating compact object surrounded by a revolving accretion disk. A distant observer sees the disk in an edge-on position. The center of the disk may be taken as the origin of $r-\theta-...
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How far can light (packets of photons) travel on earth or atmosphere?

How far can light travel on earth or in the atmosphere? Or, if I want to be more specific, how far can one photon travel until it disintegrates? I assume gravitational pull and other effects cause ...
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Shooting a single photon at a 1/2 transparent 1/2 mirror 45 degree piece of glass [duplicate]

I have very limited knowledge of any of this (read: none), but have wondered this for a number of years: What would happen if one were to shoot a single photon at a piece of half transparent / half ...
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Do emitted photons have a well defined frequency or just a spread as per HUP?

I have read this question: Conservation of Energy in photon exchange between two atoms where Kurshal Shah in a comment says: As per the energy-time uncertainty relation, the emitted photon ...
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Are photons affected by SR time dilation (velocity) or not?

Photons are massless particles. Time dilation is caused between two observers either by the relative speed of the observers or by the observers being in different gravitational zones (stress-energy ...
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Is 'photons being massless' the reason everyone observes their speed to be the same?

When a man on a train throws a ball, the resultant velocity of the ball (as seen from ground) is the sum of the velocity of the train and the velocity imparted to the ball from the throw. However, if ...
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Conservation of Energy in photon exchange between two atoms

Consider a hydrogen atom, A, in the first excited state placed at a small distance from another hydrogen atom, B, in the ground state. Now, when A drops down to the ground state, it emits a photon ...