Questions tagged [photon-emission]

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Are there names for Helium (He) emission lines like the Lyman/Balmer/Paschen series in Hydrogen?

Just wondering if helium emission lines have names like hydrogen lines. For instance the Balmer series is: $$H_{\alpha}, H_{\beta}, H_{\gamma}, H_{\delta}...$$ The Lyman series is: $$L_{\alpha}, ...
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61 views

Light matter interaction (LASER) [closed]

I don't understand how a photon energy get absorbed or emitted by a electron. when photon incident on electron it absorbs photon energy and go to excited state, and when it come down it emits energy. ...
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210 views

Times associated with Absorption and Emission Processes

I am currently reading the book "Advances in Atomic Physics: An Overview" by Cohen-Tannoudji and Guéry-Odelin. In pages 29-31 the authors discuss a two-level atom subject to a broadband radiation ...
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61 views

Photon creation operator physical realization

I am trying to self study QED so I apologize if my question seems silly. As I realize, all physical processes should stem from some "hermitian" operator in the quantum language. As it is well known, ...
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1answer
21 views

Why does wavelength coherence affect diffusion?

Not to be confused with the relationship between wavelength and photon localization. But, laser light is is able to stay concentrated over a vast distance, much more so than every-day lamp light. ...
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20 views

Database of Color Emissions

I am reading about the color Green and am wondering if there is a database anywhere listing the atoms/molecules/powders/minerals and their color wavelengths in various forms. Basically I would like a ...
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81 views

What is electromagnetic radiation (when it is not a 'wave' of EM fields or interacting locally as a photon)?

My questions are related to the question asked at Are EM radiation and EM waves the same thing?. My background is in math (my Ph.D. thesis was in geometric analysis), and I have only taken basic ...
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22 views

Why does a hot bulb filament emit photons? [duplicate]

Heating up a bulb filament provides energy to the filament material thus exciting the electrons. So how does excitation of electrons release photons generating light since excitation of an electron ...
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1answer
30 views

Free electron laser has really free electrons?

I have read this: https://en.wikipedia.org/wiki/Free-electron_laser This states that electrons are free. Now there is a debate on this site over whether a truly free electron in vacuum can or ...
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1answer
49 views

When a valence electron is excited, how fast does it move from ground state to excited state?

Imagine an atom with a valence electron becomes excited and the electron moves to a higher orbital, is this transition between ground state and excited state at speed of light? If so, since it is not ...
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21 views

Laser Detection Paint

Does there exist a paint which if a pulsed laser of ~1500-1600nm was fired at it it would emit visible light or IR Radation (3-5 micron)? I have seen up-converting inks and paints but I can't find ...
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64 views

Why does the motion of the emitter (doppler shift) impact the energy of the photons

(a) When there is a red or blue shift, is there an actual change in the energy of the photons or not? (b) If there are two observers, one moving toward the light source and one away from it, they ...
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How does photoluminescence spectroscopy work and how can it apply to quantum dots?

Does anyone have a clear explanation of how photoluminescence works? I know some of the basics, for example, that electrons are excited by photons to create excitons and when the excitons recombine, ...
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41 views

Is thermal coupling to a too cold thermal background impossible?

In (Krauss & Starkman 1999) the authors critique (Dyson 1979), and in one section argues that in the very far future cooling will become impossible because thermal contact with the cosmic ...
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21 views

fluorescence wavelength limit

My understanding is that fluorescence occurs when light has sufficient energy to excite an electron, which then emits a different photon (always with a larger wavelength) and releases the energy it ...
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4k views

Why do atoms (iron eg) glow with all frequencies of light when exposed to enough thermal radiation?

Correct me if I'm wrong, but objects (made of constituent atoms) glow with a particular frequency of light which our eyes relate to as colour. They glow when a particle in a higher energy quantum ...
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73 views

Why is visible light observed as confined to its source?

When I observe a visible light source, like the sun or a light bulb, why do I observe the light source as a confined object? Like why is the sun or a bulb or whatever seen as a confined ball of ...
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1answer
81 views

Number of photons in a range of wavelengths

I need to calculate the number of photons in a beam of light of power $P$. I know that it has constant power $P$ across the range of wavelengths $[\lambda_1,\lambda_2]$. So, for calculating this, I've ...
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4answers
241 views

What happens to the spin when photon is absorbed by an electron?

Photon is spin 1 and electron is spin 1/2, so when a photon is absorbed by an electron it is destroyed and the electron becomes excited by that amount of energy. The next moment the electron will go ...
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47 views

How/Why does heat radiation work, atomically?

In this question the relationship between characteristic spectral lines of elements and the apparently continuous emission of blackbody radiation was examined. It was suggested in the answer that ...
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Why are there no excitations by collision for the visible transitions in the Franck-Hertz experiment?

The minima of the I(V) graph for a Neon Franck-Hertz tube are approximately 20V apart from each other, this is usually explained by the fact that excitation by inelastic collision happens at about 20 ...
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48 views

Is there any difference between Photon produced from proton and electron?

I know that accelerated charged particle produces Photon but is there any difference between photon produced from a positive and negative charge?
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107 views

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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110 views

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 color of the light emitted 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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5answers
79 views

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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58 views

“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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1answer
162 views

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
99 views

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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25 views

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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1answer
54 views

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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1answer
37 views

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
63 views

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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70 views

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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68 views

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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27 views

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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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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203 views

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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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
64 views

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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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
80 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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190 views

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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401 views

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
145 views

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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35 views

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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290 views

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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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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458 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 ...