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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How can you know that 2 photons are occupying the same location?

Someone told me once that a photon can be in the same exact location of another photon. Because they are bosons and have spin 1 you can have billions of photons occupy the same location. I was ...
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How do I solve this Compton Scattering problem? [on hold]

A 0.500-nm x-ray photon is deflected through $134^\circ$ in a Compton scattering event. At what angle (with respect to the incident beam) is the recoiling electron found? In this question, our $\...
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What does it actually mean for an electron to be excited?

I've been confused on the connection between photons and electrons for a very long time. Some examples of questions I"ve asked are linked here: What produces higher frequency light? Frequency of ...
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Can a circularly polarised EM wave be deterministically found in a fixed direction?

In classical electromagnetism, a circularly polarised electromagnetic wave is described by an electric field $\mathbf E(\mathbf r, t)=\mathbf E_0 e^{i(\mathbf k\cdot\mathbf x-\omega t)}$, where $\...
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Path a photon or phonon takes in a moving medium

Lets say we have a medium with refractive index n whose velocity is given as a function of height. $v_x(y)=ay$ How would we go about finding the motion of a photon or phonon in this space from the ...
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Is it Valid to Derive $E = pc$ From the Energy-Momentum Relationship for Photons?

Given a particle with mass $m$ moving at velocity $v$, total energy is: $$E^2 = (pc)^2 + (mc^2)^2$$ Note I am not using the relativistic - rest mass convention, as I was taught to think in ...
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Frequency of light versus frequency of electron vibration

I've been trying to understand photons and light, although entirely conceptually (layman with not much of a background here, but I really want to understand this a bit better) and there's a couple of ...
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Light Polarizer for Photons

This is maybe a noob question. I read that if unpolarized light is passed through a polarizer that only allows vertical polarization, then if this light is passed through a diagonal polarizer, only ...
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Is there a difference in wavelength emission spectra of ZnS:Ag when its irradiated with protons vs. gammas?

How would I measure this, because I couldn't find this information in literature as of yet? I have neutron (to produce protons by recoil) and gamma sources, but I don't have a pure neutron source, and ...
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Does really each and every single photon leave a dot on the screen in the bright area (double slit)?

This is not a duplicate. No other answer has said anything about this specific question. I have read this question: Why does the photon strike at one or another place on the tape? where PhysicsDave ...
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Are electromagnetic waves only caused by accelerating charges?

Like the title says, are electromagnetic waves only caused by accelerating charges? Are there any other methods for the generation of photons? If electromagnetic waves are ONLY able to be created by ...
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Why emission of an electron does not depend on light's intensity?

There's something that confuses me about the photoelectric effect. In an article I read, it's stated that the emission of an electron does not depend on the light's intensity. I'm not sure on which ...
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Is the falling back to ground state of an electron what makes the electromagnetic wave, or is it the action of absorption AND falling down?

When an electron absorbs a photon, there it accelerates and thus it creates a kink in its electric field. Then, when it falls down to its normal state, it creates another kink. Here are my questions. ...
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Conductors and non-optical photons

While there seems to be plenty of information available about the photoelectric effect and the emission and absorption of photons by conductors (metals) at optical frequencies, I’ve been searching for ...
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Photon near a black hole - find distance of closest approach from impact parameter

I have the equation relating the impact parameter $b$ to the distance of closest approach $R$. $R^3 - b^2R + 1 = 0$ which can be solved in python. I have a given $b$ and have to find $R$. however, ...
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What happens to photon in photoelectric effect

In photoelectric effect, when the photon gives energy to the electron, then what happens to itself? Where does it go? For me the photon must take the place of electron after the electron escapes the ...
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Chiral preferences of photon polarization modes

Is there any experimental evidence that both photon (circular polarization) modes do indeed couple equally to both left- and right-handed fermion currents ($j_L,j_R$) ? I know it is a basic ...
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In double-slit experiments, path detection makes interference fringes disappear. How comes the detection screen does not?

One observes that the fact of detecting the location of a particle path (which slit the particle went through) entails a collapse of the particle field (interference fringes disappear on the detection ...
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Polarization of gravitational waves VS polarization of photons

This might be a stupid question, but I think i am mixing important concepts. It is well-known that gravitational waves (GWs) come in two polarizations or two states of helicity: the so called "+" and ...
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Detecting particles that do not make it through double slits, do observations match those after the slits?

I suppose we have 4 conditions to examine : { single particle | beam } * { with eraser | without eraser } I suppose we have to get the same results that those ...
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Should particle-wave duality be understood as a description of light's dual nature or as a description of two observable states of light?

In double slit experiments, light is observed in two distinct conditions (no measurement of trajectory / measurement of trajectory) that bring two different results (no interferences / interferences). ...
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What is the admissible range of sizes or scales for double slit experiments?

Sometimes, the slits are in the range of nanometers, but I often bump into comments saying you can try this at home with lasers and polarized glass. Recently, I even found clearly macroscopic pictures ...
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In quantum mechanics, which concept caters for light rays?

If photon wavefunctions are omnidirectional and don't have a definite size, how comes those from the Sun don't all collapse on Mercury and some do actually reach Earth ? I understand that ...
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Does a photon's wavelength (and energy) change when reflecting off a mirror?

The momentum of a photon is $\ p=E/c.$ When a photon reflects off a mirror, it is elastic scattering. Elastic scattering should keep the energy of the photon. But radiation pressure states, that ...
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Do photons attenuate when they reflect?

I was watching a video on solar sails and it described how the momentum of the individual photons striking the sail is planck's constant divided by the wavelength of the photon. Does this mean that ...
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Can photon Create gravitational wave when it travel through Space-time? [duplicate]

When big Explosion occurs in space it create gravitational wave. but it is possible that when photon (a packet of energy) make displacement in space-time it also create gravitational wave after all it'...
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Do photons influence charged particles? [duplicate]

As a neutrally charged particle, a photon shouldn't interact electrically with another charged particle. However, since photons are electromagnetic waves, they should interact with charged particles, ...
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Quantum eraser: How does photon detection in an interference pattern “dark spot” not affect the state of the remaining photon? [duplicate]

I have read time and time again that there is nothing mysterious going on in the quantum eraser experiment, but I can't get the math to add up. Please help me: Consider these two simplified ...
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Ward identity prohibits mass of photon

On wikipedia one can read the following statement: The photon and gluon do not get a mass through renormalization because gauge symmetry protects them from getting a mass. This is a consequence of ...
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Why the energy and momentum conservation equations do not include terms reflecting the particle nature of the photons? [closed]

It is well known that light has a dual nature. However, the energy and momentum conservation equations embody the wave aspect of light but not the material aspect of the photon. Should there be ...
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Does light have mass? Why? [duplicate]

I've been wondering whether light has mass. Yet given the wave-particle duality of light, the statement seems to be affirmative. With that, how to calculate it?
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Would wall sockets glow if human eye could see light at 50Hz?

The title is self-explanatory. I know that the electrons at the tip of Live get pushed in and out with respect to Neutral. (You shouldn't say there is no current; since there is air, a poor conductor, ...
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Photons as propagators of an electro-magnetic field

What does it mean when somebody, let's say a random person on the crosswalk waiting for the sign to go green, say that a "photon is a propagator of the Electromagnetic field"? I don't know if it's a ...
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On existence of mass in different form [closed]

(I'm a mathematician actually. This is my first question on this site. So please go easy on me if it's a trivial matter or mistake) Lately I've been thinking about special relativity. The thought ...
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What happens to the extra energy when the photon hits an electron? (+ Compton's Effect)

I understand that the electron needs a specific quantized amount of energy in order to be excited to another state. For example, hydrogen requires $10.2\ \mathrm{eV}$ for its electron to jump from $n=...
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Factor of 3 in Photon Diffusion coefficient

From definition of Diffusion coefficient: $$D = c/3(\mu_a+\mu_s),$$ where $c$ is the speed of light front, $\mu_a$ is absorption coefficient and $\mu_s$ is scattering coefficient. I wonder where does ...
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Does the photon decay due to loss of energy in a gravitational shock wave that it creates? [duplicate]

If photon has energy, it has gravity. If photon has gravity and move through space at light speed, it creates gravitational shock wave (like sonic boom because gravity move at the same speed as ...
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How does electomagnetic radiation carry information?

Radio waves travel in the speed of light. But the speed of the music being played through these waves is not equal to the speed of light. Someone answered a similar question saying it is the ...
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Different frequency electromagnetic field modes and the total photon number

I have shown part (a) using commutator rules and the fact $[\hat{a},\hat{a}^{\dagger}] = 1$. Doing this has also made it clear that for part (b), if the coupling term does not change when the ...
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What percentage of the mass/energy of the universe is in the form of electromagnetic waves? [duplicate]

Is there any theoretical framework or model that would lead to a prediction, either precise or approximate, about how much or what proportion of the universe's total mass is in the form of photons, or ...
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Derivation for number of photons assigned to to an electromagnetic field amplitude

I am trying to understand a derivation concerning the number of photons associated with an electromagnetic field which is irradiated on some probe. The point is to get a expression that connects the ...
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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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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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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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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 [closed]

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 ...