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fouad89
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Is it possible to excite a photon? Or bring it to a higher electronvolt?
Is it possible to excite a photon? Or bring it to a higher electronvolt?
if you add a magnetic field to the well would the photon get excited and move to a higher energy state ?
.gravity alters spacetime the photon is still moving in a straight line with the same energy level just that straight line is spacetime curved
How would you excite it to the next state? Wouldn't you have to annihilate it and introduce a new photon?
That just changes the normal modes - it does not change the energy-level of the photons already in it.naty1 said:just change the size of the cavity or the potential...[to change the energy state of a singe photon in a cavity?]
The magnetic field is photons. So this question is talking about photon-photon interactions, or, what we used to think of as a photon interacting with a free field.fouad89 said:if you add a magnetic field to the well would the photon get excited and move to a higher energy state ?
Quote by naty1
just change the size of the cavity or the potential...[to change the energy state of a singe photon in a cavity?]
That just changes the normal modes - it does not change the energy-level of the photons already in it.
The particle in a box model provides one of the very few problems in quantum mechanics which can be solved analytically, without approximations. This means that the observable properties of the particle (such as its energy and position) are related to the mass of the particle and the width of the well by simple mathematical expressions.
"It's nature that is bizzare, not the physics."
The particle-in-a-box model can be solved analytically fersure
+1. I noticed that too - "common sense" is what tells you the World is flat.No, it are humans that are ill-informed, not nature nor the physics are bizzare.
Simon Bridge said:"Rung-Kutta" tends to imply a shooting method - there are faster methods .. also for another thread.
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Naty1 said:I think it does affect energy...for example:
http://en.wikipedia.org/wiki/Particle_in_a_box
The particle-in-a-box model can be solved analytically fersure - but it is not a good model of actual physical systems.
You could be imagining a single photon bouncing between ideal, perfectly reflecting, walls [2]. In which case, the photon is being annihilated at each wall, and then a new one is created. (Though there is some philosophical hair-splitting over this point.) It is possible to arrange for the photon thus created to be a higher frequency than the one annihilated. I would assert that this process does not well fit the concept of "exciting a photon": it kinda means that it is the same photon that has more energy like an excited electron-in-a-box is the same electron.
Without knowledge of Pauli's Exclusion Principle one might expect electrons arbitrarily far away from one another to have identical energy levels. Pauli, however, shows that is simply impossible.
didn't you read that long thread on PF where Cox actually got into the argument himself?
That's hogwash Naty...
Synopsis [one view] :
Without knowledge of Pauli's Exclusion Principle one might expect electrons arbitrarily far away from one another to have identical energy levels. Pauli, however, shows that is simply impossible.
As atyy and others have pointed out, what Brian Cox said can be considered technically correct. But as Ken G and others have pointed out, it's important how formal QM is translated into ordinary language, because its precise relationship to nature is very much a matter of interpretation.
Anyway, I'm not knowledgeable enough to take a firm position one way or the other; but I am knowledgeable enough to keep an open mind.
When we answer questions in PF, there is this, infrequently spoken, rider that we are answering in terms of some implied model. It's reasonable to take the particular model seriously - if this were a question in high-school kinematics, we'd be taking Newtonian physics seriously.DiracPool said:My belief is that we take this wave function thing too seriously because, at this moment in the dark ages of physics, we don't have a better alternative.
soarce said:You can give more energy to a photon, for instance by inelastic scatterings: Raman scattering, inverse Compton scattering. In these processes the photon is not simply absorbed and reemitted.
One also have photon-photon scattering (Delbrück scattering) and I think that in principle the photons can exchange energy. Maybe somebody from high-enegy physics can give us a definite answer.
I can easily understand how you could end up doing that - the way beginning QM texts are written, you'd think all these transitions etc happen by magic. There is always a physical process involved - the idea is to use the model that best fits the process you are looking at (or develop one.)Naty1 said:have simply taken such explanations as I posted at face value...never really questioned them...I just took the view such an explanation is a simple extension of quantum confinement...
How you get a 1D system is to make the other two dimensions very very big, so the energy levels are quantized in one dimension only.I just skimmed Albert Messiah QUANTUM MECHANICS Chapter 3 regarding one dimensional quantized systems...[which I had in mind when I posted] to criticize my own post:
...there are no one dimensional systems,
...If the potential well is finite, there is a finite probability of the wave function NOT being reflected,
...If the potential well is infinite there is complete reflection and the energy levels are quantized...and we can't do infinite anything.
What? Where? <looks>So what about the PeterDonis explanation I posted...??
One way to confine a photon would be to have a closed space-time ... this gives you periodic boundary conditions based on some metric.As a related suggestion, how about collapsing space-time to 'rev up a photon'??
[If cosmological distance expansion redshifts radiation, seems like cosmological contraction should blue-shift??]
Cox's argument involves the Pauli exclusion principle ... not everything obeys it. Cox's example was electrons, which do. Photons don't.In another discussion:
https://www.physicsforums.com/showthread.php?t=561511
Brian Cox claims changing the energy level of a particle changes the energy level of all its counterparts...So maybe all I have to do to excite all photons is to turn on a light bulb?
I wouldn't take too seriously the models, it doesn't have to be associated to a real process. One use model to calculate things and compare them with the experiments.Simon Bridge said:When we answer questions in PF, there is this, infrequently spoken, rider that we are answering in terms of some implied model. It's reasonable to take the particular model seriously - if this were a question in high-school kinematics, we'd be taking Newtonian physics seriously.
The Feynman diagram for photon-photon scattering involves the photons being destroyed (they turn into particle-antiparticle pairs) and then getting recreated after a short interval.
I agree. Based on Feynman diagram model the photon itself may go through a virtual electron-positron pair... It maintains its identity or it keeps changing ? :)It's probably a philosophical point as to whether the exiting photons are the same photons as the incoming ones.
You can approximate something to an infinite square well if you are dealling with the low-energy configuration of a big potential - then the penetration beyond the classical limits can be safely ignored.
This sort of thing is done a lot in solid state physics.