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Questions tagged [photon-emission]

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Localization of photon

Is the photon localized at the instant of its Emission (release)? by an accelarating charge by Atom´s emission
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In diffraction When wavelength is less than slit width then does the scattered light gets absorbed & emitted from the wall or just rebound?

I know that when the slit width is less than that of wavelength then the slit will act as a point source and scatter the light in all directions. But my question is that during the scattering of ...
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What determines the colour of the light emissions in a Tokamak?

We see images of Tokamak plasma with all sorts of colours from red to purple. Why do we see any light at all, since the plasma should be so hot to have dissociated all its electrons? It is all from ...
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What stops a free electron from 'using' part of its own mass to generate radiation?

The explanation I've read on why a free electron can't emit a photon goes like this: Let there be a free electron of mass $m$ moving with constant velocity $v$. We may enter a new reference frame ...
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“For every line in absorption spectra, the corresponding emission line is present, but the reverse is not true”

I was studying atomic physics and read the line for every line in absorption spectra, the corresponding emission line is present, but the reverse is not true and I am not able to understand it ...
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Difference between emission spectrum and black body spectrum

Why is an emission spectrum dependent on the chemical composition of the body's material, but the black body spectrum is independent of the material and only based on the body's temperature? Aren't ...
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2answers
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Frequencies of photons in spontaneous and stimulated emission

A Textbook of Engineering Physics by Avadhanulu, Kshirsagar says the following about Spontaneous Emission: Photons of slightly different frequencies are generated. As a result, the light is not ...
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1answer
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Formulas re quantised energy of photons emitted by electrons

I am confused about the difference between two formulas I have come across in relation to the quantised Energy of photons emitted by electrons. $E_{mn}=hcR_H(\frac{1}{m^2}-\frac{1}{n^2})$ $E_{mn}=R*...
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Why is no radiation emitted during the final transmission in He-Ne laser in Ne atom?

During the working of He-Ne laser, I have understood everything except for the fact that no radiation is emitted when the electrons go through their final transition and reach the ground state again. ...
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Fresnel equations & emission

As part of a project work I had to derive the absorption of a thin-film stack. It was a semiconductor between two oxides on a metallic back reflector. I used Fresnel equations and optimized the ...
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2answers
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Under ideal circumstances, is it possible to construct a 100% efficient photoelectric circuit?

Lets assume some ideal circumstances: 1) The incident light has same frequency, greater than the threshold frequency (sufficient to eject inner electrons too), throughout. 2) The work function ...
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4answers
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Absorption spectra

I would like some help understanding absorption spectra, for example, by a cloud of gas in space. Photons might be absorbed if their energy matches a transition in one of the atoms or molecules in ...
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1answer
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What is the role of temperature in photon shot noise departing from Poisson?

I am trying to understand the physics behind photon shot noise and have two sources. The first is from "Photon Transfer" by James Janesick which has he following bit on photon shot noise. Signal ...
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Simple diffraction on periodic structures

I am trying to understand diffraction on periodic structured in solid state physics. Q is the source of the spherical wave. R the vector to the object and R+r the vector to the scattering centre P, ...
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Accelerated electret

An electret is something that holds an electric charge. Typically it is a piece of plastic with charges stuck inside that can't get out. Suppose you stuck an electret with a large negative charge ...
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1answer
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What would be the order of energies and wavelengths of photons emitted from different electronic transitions?

When an electron from fifth orbit falls down to first orbit, then it emits a photon of wavelength (lambda ) in Lyman region of spectrum. But if an electron jumps from fourth orbit or third orbit to ...
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Solving the Radiative Transfer Equation for Different Materials (in the Visible Light Regime)

Using the radiative transfer equation $(\vec{w}\cdot\nabla)L(\vec{x},\vec{\omega}) = -(\sigma_{a}+\sigma_{s})L(\vec{x},\vec{\omega})+Q(\vec{x},\vec{\omega})+\sigma_{s} \int_{\Omega}L(\vec{x},\vec{\...
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Proof for photon energy loss due to cosmological redshift

According to Doppler redshift, the frequency of the EM radiation decreases if the emitting object is receding from the observer - this produces the problem in the quantisation of energy - the observed ...
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1answer
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Conceptual doubts with quantum-confined lasers

So, I'm reading about quantum-confined lasers, and I think that I understand the majority of it, but I haven't conceptualized some things that I think are pretty basic. I'll leave this picture here as ...
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2answers
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Why only red hue when heating materials [duplicate]

Most of the material when heated turn red or orange or yellow, why materials don't have a tone green or blue when heated high.
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0answers
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Photon explanation of dielectric effects?

When an electromagnetic wave passes through a medium, the electric component of the wave will induce a dipole. I believe this can happen in a number of different ways, including rotating of a polar ...
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1answer
51 views

How is energy conserved in spontaneous emission?

I was reading through the section on spontaneous emission in a book by Griffiths. In it he explained that spontaneous emission is really a stimulated emission except the cause of it is the electrons ...
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4answers
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Relationship between intensity and electron emission from a metal?

Here's the question: A xenon arc lamp is covered with an interference filter that only transmits light of 400- nm wavelength. When the transmitted light strikes a metal surface, a stream of electrons ...
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1answer
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Electron Absorbing a Photon

I'm trying to understand the absorption spectrum in terms of what happens when an electron absorbs a photon. If we shine white light through a sample and use a prism to disperse the light, we would ...
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1answer
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When does an oscillating charged particle emit a photon as a result of acceleration?

As far as I know a charged particle emits a photon when it undergoes acceleration. When it comes to collisions it seems quite straightforward that a single photon is emitted with an energy related to ...
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1answer
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Can be a 'frequency funnel material' created?

Hello everybody and thank you for answering. I have an idea in my mind since a while to raise the efficiency of solar panels, but It needs of a material with a very specific property. The material ...
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1answer
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Why is $K_{\alpha,3/2}$ always more intense than $K_{\alpha,1/2}$ in copper?

Consider characteristic X-ray emission from copper. The $K_{\alpha}$ line is a doublet because of the spin-orbit interaction. But why is the $K_{\alpha,3/2}$ line always more intense than the $K_{\...
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2answers
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Is it possible to make a laser by sending sunlight through an optical apparatus?

1) Is it possible to create a laser from focused sun light by separating and using only one wavelength of light as a laser and using the proper mechanism to polarize it and make it coherent? ...
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2answers
166 views

How fast does an electron jump between orbitals?

I'm wondering what speed electrons jump from level to level. I've been told only that they emit light when doing so and need energy to be inputed in order to occupy orbitals closer to the nucleus. I ...
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1answer
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What do the numbers and letters in the “Intensity” section for strong lines (emission) mean?

NIST has a website containing various tabulated spectroscopic data, including the strong lines for various elements. For example, here are the strong lines for Helium. On that page, you can see on the ...
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How can I calculate the emission spectrum of a diatomic molecule from its spectroscopic data?

I want to model the emission spectrum of a diatomic molecule based on its tabulated spectroscopic data. I have seen papers where this has been done, but I have found no concrete formulas that give me ...
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0answers
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Two-photon absorption fluorescence of air

I'm wondering if there are any major constituents of air which are capable of undergoing two-photon absorption and ultimately fluorescing in the visible spectrum. The original wavelengths of the ...
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0answers
37 views

Better understanding two particle systems

I just started covering two particle systems and I'm really confused about a lot of the fundamentals. I'm reading Griffiths and honestly, I just need some clarification so I kinda created this jumble ...
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How many discrete bands of emission lines can fit within a given swath of the electromagnetic spectrum, and how thick will a given line be?

Is the spectrum produced by a prism-based spectral analyzer: discrete, or continous? I feel like quantum mechanics requires it to be discrete [based off of my limited understanding of the ...
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Why produces a laser coherent radiation?

Short question: Why is the light emitted by a laser coherent? Respectively, why is stimulated emission coherent? edit: How does a laser emit light in a coherent state? seems to be connected to the ...
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Emission and Absorption in color

This may be a really simple question: If electrons only absorb specific wavelengths of light and then emit them and that’s how we see color, but what happens to the other wavelengths? Without them ...
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0answers
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Can two lasers ionize a single point of air?

I am not very educated in this subject, so I apologize in advance if what I am asking is obvious/incorrect/duplicated. I am interested in volumetric displays, and was doing some research when I came ...
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2answers
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Can we use the same spectral lines for a hydrogenoid like $\rm He^{+1}$

I need to determine the transition the resulted in a wave with wavelength $4689\rm{\mathring{A}}$, from a problem I tried to solve. I know that the concerned hydrogenoid is a helium hydrogenoid: $\rm ...
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1answer
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Are Emission and Absobtion spectrum EXACT photographic negative for Hydrogen Sample?

If both are exact photographic negative, then is it true that the way an electron can deexcite (for eg.4$\to$1) in many ways like first 4$\to$3 and then 3$\to$1; absorption can too take place in ...
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Does photoexcitation cross section data exist for the states of N2?

I do have electron-impact cross sections for N2 states and ionization. BUT what about light-impact photon excitation cross sections for the A, B, and C states of N2 including their vibrational and ...
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3answers
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Where does the photon that stimulates an atom's stimulated emission come from?

When I read the concept of stimulated emission I have the following doubt. From where does the photon to start stimulated emission come from? Every book simply says that a photon with right amount of ...
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Oscillations in an emission line spectrum

From my basic physics background, I know that when an electron gets enough energy from a photon or whatever it may be, it has the capacity to jump up to a specific energy level. When it loses the ...
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1answer
36 views

How do we detect infinitely narrow emission / absorption lines within continuous electromagnetic spectra?

This always bothered me, especially in the case of absorption lines. for instance, if you have a blackbody emitting a continuous spectrum, and then a filter in front that only filters out one very ...
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2answers
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Interaction between fast charged particles & static electrons

Can somebody help me understand this section from a paper from U. Fano called "Penetration of Protons, Alpha Particles, and Mesons". $d\sigma_n$ (11) is the cross section for the interaction of a fast ...
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3answers
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Why does an electron emit a photon towards the other electron during electromagnetic repulsion?

In the Quantum Electrodynamics theory, the repulsion between electrons is caused by the exchange of photons. This exchange can be represented with the help of Feynman Diagrams, but why the electron ...
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0answers
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Limits single fluorophore, simultaneous absorption and emission

So I've been trying to find out what the limitations are for single fluorophores. What I know is that a fluorophore is excited by a photon in too a higher excited state, it then relaxes and later ...
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0answers
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Is the cause of green emission in ZnO still unknown?

I know that many researchers ascribe this emission to oxygen vacancy, but I also read some convincing articles that negate this conclusion. Is the source still a matter of controversy? I think so, but ...
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2answers
446 views

Do photons bounce at mirrors? [duplicate]

I am referring to the simple mirror. How can a photon be reflected and what does that mean? Does it instantaneously reverse direction (in the case of 180 degree bounce), does it loose energy? What ...
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1answer
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X-ray Photoelectron Spectroscopy

Is XPS already an old method? not a lot of new research is produced recently about it. Besides, you can carry out the same analysis by several cheaper methods. Do you think the chemical analysis by ...
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Why do different metals have different work functions? [closed]

Why does photo current and work function vary for different metals