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 direction of wavevector in the real hexagonal phononic lattice?

Assuming we have a 2D hexagonal lattice and its reciprocal lattice. The difference between them is that the real lattice and its reciprocal lattice have 30° rotation. So if the following image is its ...
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Could a universe exist in which all light is left-circularly polarized?

If there was a Universe with nothing but photons, and these photons were all left-circularly polarized, would it stay like this? (I know this is possible since in a lab you can create a beam of left-...
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If an event horizon never forms for an outside observer, then what do (or don't) we see in the middle area on this real image of an actual black hole?

There are a lot of questions about the m87 image on this site, non of them actually answer my question. I have read this question: Does an expanding event horizon "swallow" nearby objects? ...
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The consistency in the mass of an photon [closed]

For this particular equation, I need to know whether the mass of a photon is ever so slightly different or the exact same. If the mass of a photon was calculated by the relative momentum equation can ...
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How does the uncertainity principle apply in this situation?

A common (but, as I think, incomplete) description of the uncertainity principle is the following: You cannot determine a particle's momentum and position at high accuracy at the same time It could ...
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Wave and particle nature of light during detection in a single-photons double slit experiment

I am just a curious physics student. This question is about the nature of light. In a single-photons double slits (or multiple slits) experiment, the interference pattern or the distribution of the ...
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How we feel (perceive) exact size of object through our eyes?

Light after getting reflected from objects gets focused on retina by our lens. The images formed on retina is small, which is then sensed by our brain and depending on distance we feel size of that ...
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No even-order harmonics in alkali gases? (Intuition for “symmetry in time domain'')

The polarizability can be expanded in the from: In Alkali gases, it is said that $\chi^3$ can be nonzero, and the combination of multiple waves can produce four-wave-mixing. But what about $\chi^2$? ...
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What are extended modes?

What are extended modes? I came across this concept while reading about photonics and photonic crystal. But I am not sure what is an extended mode.
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Do photons have inertia?

We all know the example where we say that a massless box containing photons has inertia, because the photons exert pressure of the inner walls of the box. But my question is about a single photon ...
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Photoelectric effect question

I am currently working on the photoelectric effect. I had an idea that we could measure the spread of kinetic energies by measuring the current as a function of the voltage for a single wavelength of ...
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How is the size calculated of the area near a hydrogen atom that a photon must hit to ionize the atom?

I do not know of any specific other information needed to answer the question.
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Coupling of photons and SC qubits in circuit QED

I have been going through a number of articles to understand quantum circuits.I am trying to understand how a qubit gets coupled with the photons? But I am only getting answers of how a qubit gets ...
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Conservation of momentum of electron-photon pair in Bohr's Model

I was reading the book: 'Fundamentals of Physics by Halliday, Resnick and Walker', and in its 'Photons and matter waves' Chapter they discuss about the interactions of photons with electrons. ...
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What is the difference between Luminous intensity and intensity of illumination?

What is the difference between the Luminous intensity and intensity of illumination? Please explain with units and dimensions as well! I googled but I partially understood it!
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From geodesic motion of photons to Maxwell equations in curved spacetime

In curved spacetime, 1.) a photon is supposed to move along a null-geodesic, i.e., a trajectory $x^{\mu} = x^{\mu}(\lambda)$ satisfying $$\frac{d^{2}x^{\rho}}{d\lambda^2} + \Gamma^{\rho}{}_{\mu\nu}\...
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Question on negative energy solutions to the photoelectric effect

the photoelectric effect was explained by Einstein as $$\frac12mv^2=\hbar\omega - W$$ where $W$ is the binding energy of the atom that the electron is in, and $\hbar\omega$ is the energy of the photon ...
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During electron-positron collision could both spins be same oriented? If not, the more of the question is how than why

Photons, as a result of annihilation should carry information regarding the law of conservation of momentum and spin of the particles that produced them but I can not figure out what force should ...
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Understanding the derivation of photon noise from Bose-Einstein statistics

I will premise this question with the fact that I am trained in mathematics and not physics. Right now I am reading Chapter 1 of the book Optical Radiation Detectors about radiation noise in blackbody ...
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Frequency of photons and speed in media

I'd like to ask a few questions about photons, not as a professional of physics. Frequency: Since it's connected to the frequency of the wave composed by the stream of photons but can be defined for ...
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Moving Through Space-Time [closed]

Now see, photons travel through space and they don’t travel through time. And for any particle the limit to travelling through space is $c$. And at that limit it cannot travel through time. Now my ...
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Changing the relative phase of two photons in an Hong-Ou-Mandel interference produces anti-bunching?

What happens to the output of a beam splitter when you change the relative phase between two photons that enter from the two input ports? In Hong-Ou-Mandel interference for a beamsplitter of the form, ...
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Bekenstein bound busted?

The Problem Let's start with the formula in Wikipedia: I compute: $I \leqslant 4.6\times10^7 bits/eV m \cdot R \cdot E$ I chose these units because they are convenient for dealing with photons. In ...
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What is the reason for the appearance of absorption lines in the spectrum of light coming from the sun?

If your answer was that the sun's atmosphere absorbs some photons, I don't think so. Because the atom, after absorbing a photon, it seeks stability and emits an electron in a short time compared to ...
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All the information (photons) within a unit cube of space [closed]

So here is a thought, lets fix a cube of side 1cm, it contains light passing through it from all possible angles, be it stars or insect. If we change our angle of view we can see different objects due ...
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Does the oscillating electric and magnetic field of a photon generate gravitational waves?

From my understanding, little as it may be, because photons have energy they warp spacetime. The energy is expressed as an oscillating electric and magnetic field. Would this mean that the energy is ...
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Atom emits photon when electron changes energy levels — is this related to moving charge emitting e/m radiation?

Not much more than what I asked in the title. I think it is true that a moving charge emits photons also.
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In a LED the electrons from the n-type combine with the p-type which creates a photon. Are the electrons 'lost' or gone when this process takes place?

In a LED the electrons in the n-type move to the p-type where they are then 'combined' with the holes in the valence shell of the p-type which produces photons. My question is that when this happens ...
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Does light have a mass? [closed]

Could you please argue with work and gravity? Or however you like. I just don't get it. Thanks. A physics professor talked about if light had a mass, it should do work ($W=N\cdot m = \frac{kg\cdot m}{...
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How photons make us locate the position of objects?

We detect an object with the help of light. When photons hit the retina our eyes find the presence of the source of the light (object), the source being the original source of detected light or ...
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Compton scattering electron recoil energy [closed]

I need to show that the recoil electron energy is: $$ \varepsilon = mc^2 + \frac{(2\alpha \cos^2\phi)h\nu}{(1+\alpha)^2 - \alpha^2\cos ^2 \phi}$$ Where $\alpha = h \nu_0/mc^2$ and $\phi$ is the ...
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How does the black body photon distribution assume no reflections?

I understand that the definition of a black body is that it is a ‘perfect absorber and emitter with no reflections’ and while I see these properties being used to derive results in thermodynamics, ...
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Why do photons in the Casimir effect get destroyed when they collide with each other?

Shouldn't these photons create a stronger photon when they collide? If you shine a light at another light it gets stronger not destroyed. Why is it different in the Casimir effect case?
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How does light, which is an electromagnetic wave, carry information?

We see an object when light from a source strikes the object and then reaches our eyes. How does light, which is an electromagnetic wave, gets encoded with the information about the object? Do the ...
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Collision of two beams of light [duplicate]

I have been thinking about what would happen if by chance the photons collided with each other. I heard once that electromagnetic waves pass through each other without any interference. I wanted to ...
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Photons confuse me [duplicate]

I'm not entirely sure if my question is valid or not but I'll ask it anyway. So my physics porf. told us the Photons are constantly in motion and they never come at rest and the sub-topics relating to ...
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Specular Reflection of IR Light

I have started to use thermal imaging cameras more and more and realized that I can see the reflection of my self bouncing off of a glass window through the IR camera. When viewing it on my monitor, I ...
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Can we lock the light (photons) up inside a box? Why / Why not? [duplicate]

Imagine a box designed to make vacuum state inside. Is it possible for us to lock the photons up inside something completely enclosed?
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Force on a relativistic laser source

Consider a laser source emitting a laser beam in the horizontal direction. If we are given the power of the laser source, we can calculate the force on the laser beam. Now consider that the laser beam ...
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Can a single photon have circular polarization?

There are on this site a few questions about photons and circular polarization, but none of them give satisfactory answers: Connection between spin angular momentum of a photon and circular ...
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What result will we get in the alternative double-slit experiment?

My son offered me a description of the experiment First, the photon passes through double-slit. If the photon passes through the first slit it goes to BBO1. This crystal converts the photon into a ...
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Non-quantum explanation for Mach-Zehnder interferometer effect

The phenomenon of all photons being detected at only one detector seems quite reasonable to me, classically. If a photon gets deflected at the first beam splitter for whatever reason, it gets ...
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Can a photons wavelength be independent of its associated temporal wavefunction?

Typically a traveling photon is described as being in a superposition of frequency modes $\hat{E} = \int g(\omega) a^\dagger_\omega d\omega + h.c. $ where often the $g(\omega)$ is some kind of pulse. ...
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Do gravitational waves change the color of light?

It stands to reason if gravity changes the color of light then the color will be affected by gravitational waves. My question is, when the waves pass, will the color change be permanent or will the ...
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What happens to a photon that gets cut?

This is about photons of very large wavelength, say radio frequencies on the lower end of the electromagnetic spectrum. Given a wavelength of several hundreds of meters, it seems to me the carrying ...
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What does Stokes's Rule explain in regard to photons?

What process does it describe and does it break the Conservation of Energy? For more details, Stokes's Rule is mentioned in Einstein's Proposal of the Photon Concept. His dissertation about Stokes's ...
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How do photons affect each other gravitationally?

Photons are energy. According to general relativity they should bend space. Assuming two photons pass one another in a large void of empty space how would they gravitationaly affect each other ...
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Is solar radiation at earth's surface sufficient to eject electrons from aluminum?

Is solar radiation at earth's surface sufficient to eject electrons from aluminum?
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Why does light bend at an angle when it passes through a prism?

i mean when the light go throw the prism it Deviates. At an angle and dissolves at the same time. Do prism atoms have anything to do with this? why it can't go directly in a straight line?
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Entropy in a system constitute by an atom and a photon

Suppose that we have an atom $A$ in an excited state. This atom has a probability of emitting a photon $\gamma$. If we are in a finite space there is a probability that the atom $A$ absorbs the ...

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