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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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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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140 views

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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2answers
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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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22 views

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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124 views

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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1answer
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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 ...
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Energy of a light wave

I know that the energy of a photon can just be found from the equation E = hv. However, if we measure light as a wave, can the energy be found from the amplitude rather than the frequency, like you ...
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How does $H^2$ effect on the probability of photon detection?

Lets consider an electromagnetic wave, between two ideal conductive plates. Maxwell's theory predicts appearance of a standing waves(of $\textbf{H}$ and $\textbf{E}$), at that nodes($\textbf{E} = 0$)...
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Are all the photons we observe from the sun disappearing beyond the horizon only reflected ones?

On a boat in the ocean at the equator (earth rotating 28km) watching the sun dip below the horizon (4.7k away) do we see any photons that were emitted directly from the sun (8 minutes ago) or are they ...
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Existence of Photon

I was reading Feynman lectures on physics (volume 1) when I encountered the following paragraph: Returning again to quantum mechanics and fundamental physics, we cannot go into details of the ...
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Oscilloscope recording of single photon

What would happen if we had super fast and super sensitive oscilloscope that could probe and record into memory electric or magnetic field oscillation created by single photon that would fly near the ...
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Why do photon only interact with atoms whose electronic orbitals are at very particular energies? [duplicate]

From https://www.sciencealert.com/physicists-made-a-new-part-matter-part-light-particle-with-a-shake-of-an-atom: Photons - those fundamental particles of light - have a slew of interesting ...
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What are the properties of light in the wave/ particle theory that map to properties we physically observe?

When we see two beams of light of different colours, what is different about them in the wave theory? And what is different about the photons that make up each of them? When we see two beams of light,...
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Will a free neutron radiate if it is decelerated?

In this answer it is said (and I fully agree): Yes, a ... photon can accelerate a lone neutron. The kinetic energy imparted to the neutron reduces the photon's wavelength (redshifts it) by the same ...
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Can a photon transmit a momentum to a neutron? [duplicate]

Is a photon able to transfer an impulse to a neutron or, and this is the same, can light accelerate a neutron?
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How far can radio waves travel in vacuum? and light waves?

Radio wave and light wave are the same thing. They all are electromagnetic radiation, the only difference between them is frequency. My question : 1, is there any photon-like thing for radio wave? 2, ...
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How many photons are emitted by a lightning strike?

As the title suggests, I'm curious to know, approximately how many photons are emitted in a single lightning strike?
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Do photons interact or not directly?

All I am asking about is photon (EM wavepacket) photon (EM wavepacket) interaction. I have read this question: If photon-photon interactions are impossible, how are higher harmonics generated? ...
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What stimulates pair production? [duplicate]

I read that it happens when passing a nucleus or an electron, but why does that cause pair production to take place?
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Can one of the photons that is produced in annihilation recreate the same particle/antiparticle in pair production?

If a particle and antiparticle collide (in annihilation) to produce 2 photons, each with energy x, would you need a different photon of energy 2x (in pair production) to recreate this particle and ...
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What is the difference between $n $ (no. of photons passing a fixed point per second) and $f$ (frequency) of a photon in the formula: power = $nhf$?

As above. As far as I understand, the frequency of a wave is also the number of waves passing a fixed point per second.
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Are Bremsstrahlung and the Unruh effect equivalent?

This paper argues that the absorption and emission rates from and to the thermal Unruh bath of a proton viewed in a coaccelerated frame is equal to the emission rated viewed from an inertial observer. ...
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What are zero-energy Rindler photons?

In the discussion of the Unruh effect and Bremsstrahlung (e.g. here) I always come across "zero-energy Rindler photons". What exactly are these? Shouldn't a zero-energy photon correspond to a static ...
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Is the highest photon energy currently possible a Planck photon or based on space-time quantinization?

It makes sense that there could be an upper limit to the frequency/energy for individual photons if the universe as we know it is quantized. But, the highest energy photons I've heard about have a ...