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Energy of an electron


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#1 Sriman Dutta

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Posted 31 December 2016 - 09:14 AM

Hi everyone,

 

Suppose that there's an electron at rest removed from all gravitational sources and any other fundamental particles. There's an observer who is revolving around the electron at a distance of d. But, due to lack of reference points, the observer cannot say with certainty that he is revolving or the electron is. He assumes that the electron is revolving. According to the Larmor's Formula, the observer will find energy being radiated out by the electron since he observes it revolving. But, how can the electron radiate out energy if it's not revolving? So, will the observer record no energy?


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#2 derek w

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Posted 31 December 2016 - 11:55 AM

All particles have a field.


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#3 swansont

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Posted 31 December 2016 - 12:22 PM

Hi everyone,

 

Suppose that there's an electron at rest removed from all gravitational sources and any other fundamental particles. There's an observer who is revolving around the electron at a distance of d. But, due to lack of reference points, the observer cannot say with certainty that he is revolving or the electron is. He assumes that the electron is revolving. According to the Larmor's Formula, the observer will find energy being radiated out by the electron since he observes it revolving. But, how can the electron radiate out energy if it's not revolving? So, will the observer record no energy?

 

 

Acceleration is not relative. The electron will not be radiating.


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#4 Sensei

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Posted 31 December 2016 - 01:01 PM

Suppose that there's an electron at rest removed from all gravitational sources and any other fundamental particles.

 
Any particle with rest-mass (unlike massless particles) can be at rest in its own rest frame of reference.
https://en.wikipedia...wiki/Rest_frame


There is also such frame of reference, center of mass,
in which either object is moving.
https://en.wikipedia.../Center_of_mass
https://en.wikipedia...-momentum_frame

Earth doesn't revolve around the Sun, but Earth revolve around center-of-mass of entire Solar System, so the same the all other planets.
Majority of the Solar system mass is in the Sun, so center-of-mass of Solar system is located close to the star core.
But in binary star system it could be not true anymore.

BTW, it's used to find out whether distant stars have planets.
https://en.wikipedia...er_spectroscopy


Edited by Sensei, 31 December 2016 - 02:03 PM.

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#5 studiot

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Posted 31 December 2016 - 01:19 PM

 

 

Acceleration is not relative. The electron will not be radiating.

 

Just to pick up on swansont's point;

 

You need to distinguish between translational (accelerating) motion which classically leads to radiation by a charge and rotation or (accelerating) angular motion which does not.

 

I say classically because with the correct boundary conditions in quantum mechanics the translational motion does not lead to radiation.


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#6 Sriman Dutta

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Posted 31 December 2016 - 05:26 PM

So no energy is recorded.


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#7 swansont

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Posted 31 December 2016 - 07:32 PM

Just to pick up on swansont's point;
 
You need to distinguish between translational (accelerating) motion which classically leads to radiation by a charge and rotation or (accelerating) angular motion which does not.
 
I say classically because with the correct boundary conditions in quantum mechanics the translational motion does not lead to radiation.


Angular motion does, too. Cyclotron radiation.

Of course, an electron "rotating" is a misguided notion, as it's a point particle. But send it on a curved path, and it will radiate.
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#8 studiot

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Posted 31 December 2016 - 07:44 PM

Angular motion does, too. Cyclotron radiation.

Of course, an electron "rotating" is a misguided notion, as it's a point particle. But send it on a curved path, and it will radiate.

 

Is an electron traversing a 'curved path' translating or 'spinning on its axis'?


Edited by studiot, 31 December 2016 - 07:44 PM.

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#9 swansont

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Posted 31 December 2016 - 07:48 PM

 

Is an electron traversing a 'curved path' translating or 'spinning on its axis'?

 

 

 

When the lines between classical and quantum are blurred like this, it's unclear what one means or how it will be interpreted.


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#10 studiot

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Posted 31 December 2016 - 07:51 PM

 

 

 

When the lines between classical and quantum are blurred like this, it's unclear what one means or how it will be interpreted.

 

I can't see it.

Either something moves from A to B or it does not.

If it does then translation is involved, regardless of what else happens.

 

It doesn't really matter whether that something is a blurred wavelet, a quantum particle or something really esoteric.


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#11 swansont

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Posted 31 December 2016 - 08:10 PM

I can't see it.
Either something moves from A to B or it does not.
If it does then translation is involved, regardless of what else happens.
 
It doesn't really matter whether that something is a blurred wavelet, a quantum particle or something really esoteric.


Electrons in an atom do not have defined trajectories. You can't say anything about how they got from one point to another, if you were to localize them at two different points in time. But the OP isn't talking about that. It was, however, talking about a rotating electron. How does one interpret that? And how does one make a clear answer to anyone who thinks a rotating electron isn't nonsensical? So you don't see it, because you know the subject matter, but you aren't the only one reading the answer.
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#12 studiot

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Posted 31 December 2016 - 08:17 PM

Electrons in an atom do not have defined trajectories. You can't say anything about how they got from one point to another, if you were to localize them at two different points in time. But the OP isn't talking about that. It was, however, talking about a rotating electron. How does one interpret that? And how does one make a clear answer to anyone who thinks a rotating electron isn't nonsensical? So you don't see it, because you know the subject matter, but you aren't the only one reading the answer.

 

Upon re-reading the OP I find the same interpretation as I originally made viz heliocentric v geocentric motion argument applied to the electron/observer system, clearly considered as a miniature Earth/Sun system.

 

This is why I replied as in post#5 clearly identifying and underlining a classical response, but drawing the distinction between this and a quantum response.

 

As a matter of interest do you think a quantum electron changing its energy level by tunneling in a semiconductor without changing its position in the lattice emits EM radiation?


Edited by studiot, 31 December 2016 - 08:18 PM.

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#13 Sensei

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Posted 31 December 2016 - 08:40 PM

Electron bound in atom is pretty specific case,
hard to make experiment,
but free electron emitted by electron gun,
https://en.wikipedia...ki/Electron_gun
fired at target, has significant velocity and kinetic energy..
 
If we pass free electrons through hole in electron gun's positive charged electrode, they will fly freely..
 
Then their trajectories can be bend,
by electric or magnetic fields.
So one can put there electromagnets on the top, bottom, left and right, of vacuum chamber..
And bend electrons trajectories,
and call it CRT.
https://en.wikipedia...athode_ray_tube

Electrons accelerated to significant velocity/kinetic energy have to lost their energy (decelerate) prior riching "out frame of reference", and release their energy by emitting photons with appropriate energy.

Edited by Sensei, 31 December 2016 - 08:59 PM.

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#14 zztop

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Posted 1 January 2017 - 01:10 AM


Electrons accelerated to significant velocity/kinetic energy have to lost their energy (decelerate) prior riching "out frame of reference", and release their energy by emitting photons with appropriate energy.

Electrons do not emit photons, the atoms of phosphorus coating the CRT do.



#15 Sriman Dutta

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Posted 1 January 2017 - 04:52 AM

Electron transition releases energy.

 E_2 - E_1 = hf


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#16 StringJunky

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Posted 1 January 2017 - 09:00 AM

Electron transition releases energy.

 E_2 - E_1 = hf

Photons.


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#17 Sriman Dutta

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Posted 1 January 2017 - 09:59 AM

Yes. Energy in the form of photons.


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#18 zztop

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Posted 2 January 2017 - 05:38 AM

Electron transition releases energy.

 E_2 - E_1 = hf

These are the electrons transitioning between the energy levels WITHIN the atoms of phosphorus coating the CRT screen. NOT the electrons coming from the electron gun as "Sensei" incorrectly posted.



#19 MigL

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Posted 3 January 2017 - 08:05 PM

Either or, makes little difference to the OP.

 

The OP inquired about the equivalence ( ? ) between an observer revolving around a stationary electron, versus a spinning electron with a stationary observer.

Aside from the fact that the revolving observer is undergoing acceleration and there can be no equivalence between the two cases, the notion of a spinning, POINT particle is non-sensical ( or at least ill-defined ).

Swansont has already mentioned this a few times.


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#20 swansont

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Posted 3 January 2017 - 08:51 PM

If we ignore the quantum contradiction here and instead assume we had a microscopic ball on which charges were placed, the ball would radiate if it were rotating.


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