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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 the Detector in the double slit experiment and how it works?

What about the "DETECTOR". Is it a passive device or is it just a fictional mathematical prob. I think that detector is somehow consuming the energy responsible for the wave nature of the photons, ...
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How do quantized photons interact in an interferometer?

Since light is quantized into photons, how can a single rare photon entering one side of a large, [say, 100 meter wide], interferometer from a very dim star, a phton which is only in the ...
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Do photons exist at all possible wavelengths? [duplicate]

My question refers to Photon flux spectrum diagrams. The diagram shows the number of photons at different wavelengths. My question is whether the graph is granular or continuous. Do photons exist at ...
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Yukawa form of electrostatic potential with $\mu_{\gamma} \neq0$ (photon mass)

Yukawa form of electrostatic potential with $\mu_{\gamma}\ne 0$ (photon mass) is: \begin{equation} \varphi(r)=a\,\frac{e^{\mu_{\gamma}r}}{r}+b\frac{e^{-\mu_{\gamma}r}}{r} \end{equation} Since this ...
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change frequency of monochromatic light without altering source?

When light goes from one medium to another its wavelength and velocity change while frequenccy remains the same. Also $E=h\nu$ ie.Frequency depends on energy, Now, given a light beam of given ...
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What happens to the energy of an absorbed photon?

Photons are electromagnetic wave fields that travel at the speed of light. When they are absorbed by an object, their momentum and energy is transferred to the absorbing object. What is that ...
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Why do we believe local gauge invariance (that tells us photons are exactly massless)? [duplicate]

There are experimental upper limits on the photon's mass, but they are finite. I heard that the reason we know that photons have exactly zero rest mass (and thus travel exactly at the universal ...
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Double Slit Experiment : Photon vs Electron

are the following statements correct: For Young's double slit experiment with electrons, the separation between two slits has to be smaller than the position uncertainty of the electrons. But no ...
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Experiment to determine if a photon is emitted in one direction

I am currently puzzled over one aspect of the notion of photons regarding its property of being localized and having a direction (as opposed to the classical EM picture of a spherical wave). I have ...
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How does a single photon behave propagating through glass?

Take a normal pane of window glass and a photon somewhere within the visible range. My limited understanding is that when light passes through glass one shouldn't think of little spheres travelling ...
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What about the way photon's bounce of a surface causes a human to interpret an image? [closed]

I have read online that we interpret an image based on photons entering our eyes and some technical stuff. But I am still unclear about how photons bouncing on different surfaces can be so different ...
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Elastic X-ray diffraction: Where does the Photon Momentum go to?

lately I was discussing the following situation. Let's suppose you are doing X-Ray diffraction experiments on a crystal. So what you basically do is shooting a high energy photon with a wave vector $k$...
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Light from an incandescent lamp

In a tungsten filament lamp, electrons travel through a high resistance path,due to which the temperature is increased. Now why does it emit light , is it because of the transitions of electrons from ...
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If a photon is powerful enough, will it not pass through glass?

So I know how glass works, it has a large electron gap so the photons that hit it don't have enough energy to move the electrons into a high energy state and instead pass through because the amount of ...
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Questions regarding photons and distance contraction

I've got a few question regarding photons and lorentz contraction. they may be really stupid questions (I am not a physicist). But they have been bothering me for a while. 1. Is Lorentz distance ...
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Order of Magnitude for Photon Induction

What does magnetic induction look like when we imagine just one photon passing by? I'm imagining some sort of coil wrapped around the edge of a waveguide or something so that it picks up some of the ...
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Are all collisions involving photons and electrons elastic?

In my textbook it asks me to calculate the energy gained by an electron that scatters an incoming x ray through a given angle. Using the Compton scattering equation you can work out the change in ...
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Time-of-flight spectroscopy and energy-time uncertainty

I am a bit confused about spectral and temporal filtering of light. I consider a single-photon source of a bandwidth of $1\,$nm at $1550$ nm. That means, that the wavelength of the emitted photons ...
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Do photons have any relativistic mass?

In some books I found they are writing photon momentum $mc$ rather than $E/c $. Which one is right? But if I put $v=c$ in relativistic mass equation, $$m=\frac{m_0}{\sqrt{1-v^2/c^2}},$$ it becomes ...
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What are the Basic Properties of a Photon?

I want to grasp the idea of a photon. While researching, I have come upon many different ways of describing a photon, but have found "quantum of the electromagnetic field" to be most satisfying. ...
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Velocity vectors during the propagation of photon in elastic scattering question [duplicate]

I have been trouble with the concept of energy of the photon during propagation in random scattered or random continuum medias. E = hf, where E is the energy of the photon in Joules; h is Planck's ...
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Question about quanta and $E=h\nu$

It is my understanding that Planck's major breakthrough was that energy comes in the forms of 'packets' called quanta, each of which has the energy of $6.62e-34$ of one Joule. By looking at Planck's ...
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Cavity optomechanics Hamiltonian

In cavity optomechanics the radiation pressure exerted by light moves a mirror in a cavity. Because of that the resonance frequency of the cavity changes due to change in length of the cavity (cavity ...
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Why does a scintillator need to be fast decaying?

I have two scintillators, say, one with a decay time of 1 ns vs. one with 100 ns. All other parameters like light yield, size of crystal, electronics used, source emission rate, are the same for both. ...
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penetration of Fe55 X-ray photons through glass

Can X-ray photons from Fe55 (one radioactive isotope of iron) pass through glass ?
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How much energy can you store in a quantum resonator?

Does it decay according to a fixed formula? What determines the limit to how much light you can pump in? Could you build a really big one and store all of a cities excess energy?
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Brehmsstrahlung radiation query - If an electron is constantly being decelerated, how does it emit a photon with a fixed energy?

According to my textbook they simply say an electron is decelerated by a nuclei and this means it loses KE. The difference in KE is given off as a photon. But an electron is always being pulled back ...
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How to calculate the distance that 1-10 KeV x-rays have to travel in air to lose 90% of its energy?

I'm trying to calculate the distance of air that can strip a beam of 1-10 KeV x-rays from 90% of its original energy. I came across this graph which shows the mass attenuation coefficient of air, but ...
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Do photons move as waves [duplicate]

Photon. I am curious about the movement of photons.Do they move in wave motion (up and down) or do they move in straight lines
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Photon will deform through time? [duplicate]

Is it possible that photon will deform through time? so after millions of years a single photon will get redshifted? Can we test this possibility by current technology? If this is true, what ...
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Energy-frequency dependency of a photon and its medium of propagation

Is the equation relating a photon's energy to its frequency the same regardless of its medium of propagation? And for the equation relating its momentum to wavelength as well?
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Distribution of photons given an EM radiation

Given some EM radiation in vacuum, how can we calculate the probabilities or distribution of photons of different wavelengths? How might the results of the calculation change if the entire radiation's ...
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Why is glass really transparent? [duplicate]

Glass is an amorphous polymorph of silicon dioxide, melted and quenched so that grain boundaries grow uniformly and are small with respect to visible light. Its an oxide not a metal and has a large ...
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Relativity and Momentum of photons

I read somewhere that as the speed of a particle approaches c, its mass tends to infinity. Light is composed of particles (photons). If that is the case, then why don't we feel an enormous weight ...
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Why doesn't there exist a wave function for a photon whereas it exists for an electron?

A photon is an excitation or a particle created in the electromagnetic field whereas an electron is an excitation or a particle created in the "electron" field, according to second-quantization. ...
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Photo-electric effect with light reflected from a blue wall

Suppose we have a metal which has a work function corresponding to yellow. Obviously, if light with frequency greater than yello is made to fall on it, it would show photo-electric effect.Now, ...
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How can photons excite multiple atoms in a szintillator?

For a photon to excite an electron of an atom it typically has to have the exact right amount of energy for the transition. When the photon energy is to low it is pretty clear that the transition can ...
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Scintillator decay time=1000 nsec,does that mean dead time is really high?

What I'm really confused about is, say my scintillator is really slow, and has a decay time of about 1000 nsec. Does that mean, if one neutron is being read by the electronics, for that particular ...
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Are there ways to detect/measure photons that don't involve electrons?

As per question, are there ways to detect photons, and/or to measure their energy, that don't involve any interaction with electrons? And if yes, are there detectors which use photon interactions with ...
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Radiation pressure and conservation of energy

TL;DR: How can radiation pressure conserve energy, if we consider the case where the atom absorbs all the Energy of the incident photon via its newly excited electron, and stills gains additional ...
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Quantum equations for interaction between two charged particles

Reading in wikipedia about quantum mechanics, standard model of particles, ... . I'm asking myself about the electromagnetism from a quantum particles point of view. Assuming two "fixed" charged ...
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What particle is created when a B- or E-field operator acts on the vacuum

I have some conceptual trouble understanding what the different field operators in QED do. According to Wikipedia, the field operators are given by $\mathbf A(\mathbf{r} )=\sum _{\mathbf {k} ,\mu }{\...
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Comprehensive Nature of Light: Transverse vs Longitudinal Waves and Ray Optics

----------I understand that we consider light as a transverse wave in the sense that light is composed of E&M fields oscillating perpendicular to each other and the direction of propagation. And I ...
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Why do atoms emit a certain colour of light? (The emission spectra)

We were taught about the emission spectra in class last year, but my teachers couldn't give me an answer to 'what determines the colour of light emitted?'. (they were giving me the answers to the ...
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Does $PV\propto T$ apply to a photon gas?

For an ultrarelativistic ideal gas, I know that $p=\frac{u}3$; $TV^3 =$ constant; $pV\propto T$. For a photon gas, I know that the first two results apply as well. However, I am unsure if the third ...
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Does hydrogen reflect all visible wavelengths other than the wavelengths it absorbs?

I'm confused how reflection and absorption of photons work. For example hydrogen absorbs 4 wavelengths of light, but then that energy is emitted once the electron falls back to its ground state. So ...
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Photon speed is it the same as light speed? [closed]

The speed of light is about 186000miles per sec. however, the light is also a wave. If the photon follows the wave path, then to progress at 186000miles / sec. in a linear direction must be ...
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“Interaction-Free” measurement involving statistical mixtures

What happens in the standard "interaction free measurement" when the detector connected to a bomb is replaced with attenuation (where light is lost through a semi-transparent medium)? Consider the ...
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Do polarizers also shift the phase of light?

When does passing through a polarizer change phase besides just changing polarization? Consider three cases: A polarizing beam splitter (PBS) is a clear case. Horizontally polarized light leaves ...
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Number of photons in range of frequencies

I was trying to calculate the number of photons emitted by a light of constant power $P$ between frequencies $\nu_1$ and $\nu_2$. I have already checked this question but the reply marked as correct ...