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Author Topic: What is the difference between an electron and a photon?  (Read 18443 times)

Offline percepts

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I'm trying to visualise this and the both seem to me to be a "disturbance" (for want of a better description) in the electromagnetic field so what differentiates them?


 

Offline chiralSPO

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Re: What is the difference between an electron and a photon?
« Reply #1 on: 11/07/2014 16:42:41 »
A photon has no charge--there is an oscillation in the electric field, but it averages out to zero. An electron is negatively charged, always having exactly the same charge. Also, while photons have no rest mass, electrons do. There are other differences too (like spin), but these are the most easily explained.
 

Offline acsinuk

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Re: What is the difference between an electron and a photon?
« Reply #2 on: 13/07/2014 15:36:08 »
Photons are a volume of vibrating AC magnetic energy that can helix forward at the speed of light.
Electrons are DC charged particles that move only relatively slowly.
CliveS
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #3 on: 13/07/2014 17:42:34 »
Quote from: percepts
I'm trying to visualise this and the both seem to me to be a "disturbance" (for want of a better description) in the electromagnetic field so what differentiates them?
The difference between particles can be determined as the difference in all the properties that particles have. For example; a particle has a proper mass, proper life time, is either a fermion or a boson defined as follows

Fermion: Any particle characterized by Fermi-Dirac statistics and following the Pauli exclusion principle. Two or more fermions cannot occupy the same quantum state

Boson: Any particle characterized by Bose-Einstein statistics. Two Bosons can occupy the same quantum state.

A photon is a boson whereas an electron is a fermion. An electron has charge whereas a photon has no charge. Since a photon has zero proper mass it can do what all particles with zero mass do, i.e/ travel at the speed of light (although a photon travels at the speed of light by definition).
 

Offline jccc

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Re: What is the difference between an electron and a photon?
« Reply #4 on: 15/07/2014 07:48:44 »
Electron is a charged particle, it has mass. Photon is an imaginary particle that has no mass no charge.

When an electron at rest, it produces nothing. When it moves, its force field moves.

The force field movement is light wave/EM wave. Mainstream science call it photon.

If photon is particle, when light passing glass or water slowing down, moving into air again, how it regained original speed?

Glass or water atoms absorb photon and emit another one in the same direction?

What's the mechanism? Sounds like magic not science.
 

« Last Edit: 15/07/2014 09:27:07 by jccc »
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #5 on: 16/07/2014 05:46:04 »
Quote from: jccc
Photon is an imaginary particle that has no mass no charge.
Since this part of the forum is for main stream science you need to put those kinds of speculations in the New Theories section since mainstream physics considers photons to be absolutely real, imaginary in no sense of the term whatsoever.

Quote from: jccc
When an electron at rest, it produces nothing. When it moves, its force field moves.
That is incorrect. A field does not move. Only the source that produces the field moves. An electromagnetic wave is not a moving EM wave either. Itís merely a time varying field that is the Fourier series of a sum of time varying fields.

Itís a common mistake to think of field lines as moving. The concept of the field was created by Michael Faraday so as to visualize the electric and magnetic field. Field lines donít really exist although the fields themselves really do exist. Calculation errors can easily arise when one thinks of field lines as moving.

Quote from: jccc
The force field movement is light wave/EM wave. Mainstream science call it photon.
That is incorrect. That is not what a photon is. A photon is a quantum of electromagnetic radiation and easy to detect. In very dim light a very sensitive eye can detect a handful of photons. Theyíve been studied for over a hundred years now and have a very solid theoretical basis.
Quote from: jccc
If photon is particle, when light passing glass or water slowing down, moving into air again, how it regained original speed?
Because the last atom that emitted it released it into a vacuum and any photon that moves in a vacuum moves at the speed of light = 3x10^m/s.

Quote from: acsinuk
Photons are a volume of vibrating AC magnetic energy that can helix forward at the speed of light.
That is incorrect. A photon cannot be said to ďbeĒ energy (although you phrased it slightly different as Ďphotons are a volume of Ö energyí so itís the same thing). Just like electromagnetic fields and waves they ďhaveĒ energy, i.e. itís a property of an EM field or EM wave.

Photons also donít ďhelix forward.Ē That notion comes from an elliptical or circularly polarized light. The tip of the field vector of the EM wave moves in a helix but thatís merely a mathematical description. There is no physical reality to it.

It the term AC doesnít apply here. AC stands for ďAlternating CurrentĒ. Thereís no current to speak of because thereís no charge in motion and just because something alternates with time it canít be taken to mean that itís an alternating current.

Quote from: acsinuk
Electrons are DC charged particles that move only relatively slowly.
CliveS
Thereís no reason to assert that electrons move ďonly relatively slowlyĒ since some of them move arbitrarily close to the speed of light in particle accelerator labs.
« Last Edit: 16/07/2014 05:49:30 by PmbPhy »
 

Offline jccc

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Re: What is the difference between an electron and a photon?
« Reply #6 on: 16/07/2014 06:22:41 »
Pete, I asked you what's the mechanism of electron emit photon, how electron emit different photons? Why photons travel at c in vacuum? What is energy level?

Mind to give some light? Appreciate.

 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #7 on: 16/07/2014 07:01:23 »
Quote from: jccc
Pete, I asked you what's the mechanism of electron emit photon, how electron emit different photons?
Donít you understand that itís not the job of physics to find the mechanism to how things work? While at times itís able to accomplish such a feat itís not the goal. Too many people make this mistake and then blame the scientist for it when all the time itís their misunderstanding. Thatís why it has such a high Crackpot index. See The Crackpot Index at http://math.ucr.edu/home/baez/crackpot.html
Quote
17. 10 points for arguing that while a current well-established theory predicts phenomena correctly, it doesn't explain "why" they occur, or fails to provide a "mechanism".
An electron cannot emit a photon. If it did that would mean that the proper mass of the electron was greater than it was after it emitted the photon. Since the electron has no internal structure which can be changed to accommodate the increase in internal energy it follows that the proper mass canít be different so the electron cannot emit a photon.

Quote from: jccc
Why photons travel at c in vacuum?
Thereís several ways to look at it

* Itís a postulate Ė This means that we accept that itís true and observe that itís true but we donít know why itís true. Thatís the second postulate of special relativity. Itís the same thing as saying that the proper mass of a photon is zero.

** Postulate that the rest mass of the photon is zero. It then follows that Maxwellís equations take their typical form and in a vacuum the electromagnetic wave moves at the speed of light c. https://en.wikipedia.org/wiki/Wave_equation Since photons are the quantum of light it follows that they too must travel at the speed of light.

Quote from: jccc
What is energy level?
The energy level of what?
 

Offline UltimateTheory

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Re: What is the difference between an electron and a photon?
« Reply #8 on: 16/07/2014 15:37:44 »
An electron cannot emit a photon. If it did that would mean that the proper mass of the electron was greater than it was after it emitted the photon. Since the electron has no internal structure which can be changed to accommodate the increase in internal energy it follows that the proper mass canít be different so the electron cannot emit a photon.

Electrons emit photons all the time...

They just need enough kinetic energy to emit photon.
In this experiment they have few thousands electron volts kinetic energy:




Free electron is emitting photon 13.6 eV (or sum of photons energies 10.2 eV + 3.4 eV + ....) and is intercepted by free proton.
 

Offline percepts

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Re: What is the difference between an electron and a photon?
« Reply #9 on: 16/07/2014 18:58:12 »
Thanks for replies. All being read and absorbed.
 

Offline jccc

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Re: What is the difference between an electron and a photon?
« Reply #10 on: 17/07/2014 02:11:19 »
In quantum field theory, fields are things that permeate all space and time.  The "electromagnetic field generated by an electron" is described by the electron coupling to this background electromagnetic field and changing it.  The electron doesn't create the field, but rather creates a disturbance in the field that we call "the electromagnetic field of the electron."

You can think of it loosely like boats on an ocean: the ocean is the background field and would exist even in the absence of boats.  The boats are like particles, which interact with the ocean and can disturb it.  The boats don't generate the ocean, but they do generate particular disturbances on the ocean.

Maybe the above explains the mechanism how electron able to emit photon?
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #11 on: 17/07/2014 05:12:27 »
Quote from: UltimateTheory
Electrons emit photons all the time...
You're either confusing photons with virtual photons, a common misconception or with the photons generated when electrons are accelerating. In the former case QED vertex

c1965b74adb3dfa3752211039e4edc58.gif

by itself does not represent a possible physical process, the reason being purely kinematical: c1965b74adb3dfa3752211039e4edc58.gif would violate conservation of energy. In the center-of-mass frame the electron is initially at rest, so its energy is 2799d3215bc1b5dc7f4cdd1a8c7a044a.gif. If the electron was to emit a photon then in that same frame, where we started out with zero energy, there would be the energy of the rest mass of the electron 2799d3215bc1b5dc7f4cdd1a8c7a044a.gif plus the energy of the photon, thus violating  conservation of energy.

In the later case the electron only facilitates the process of creating photons, it doesn't emit them.
Quote from: juccc
Maybe the above explains the mechanism how electron able to emit photon?
You're confusing real photons with real photons.
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #12 on: 17/07/2014 06:01:08 »
Quote from: UltimateTheory
Electrons emit photons all the time...

They just need enough kinetic energy to emit photon.
In this experiment they have few thousands electron volts kinetic energy:


I just looked at the link to that photo. It's a Crooke's tube. You don't understand how it works and your misunderstanding of it has led you to use it to support your flawed idea that electrons emit photons.

Please go to the Wikipedia site and read how a Crook's tube works. You'll see that there is a difference of potential set up between the anode and cathode thus creating an electric field parallel to the axis of the cylinder of the tube. As ions (not electrons) accelerate along the tube's axis they collide with the atoms which make up the gas in the tube. When the atoms de-excite they emit photons.
 

Offline jccc

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Re: What is the difference between an electron and a photon?
« Reply #13 on: 17/07/2014 06:22:02 »
Knock rocks in dark, you can see light. Even rub blanket in dark I can see spark/light.

I believe/understand the electrons got exited by the force applied on rock or blanket atoms, produce EM wave in quantum field. light or photon as we call it.

Am I correct so far?
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #14 on: 17/07/2014 06:56:45 »
Knock rocks in dark, you can see light. Even rub blanket in dark I can see spark/light.

I believe/understand the electrons got exited by the force applied on rock or blanket atoms, produce EM wave in quantum field. light or photon as we call it.

Am I correct so far?
No. Each example that you gave emits photons for different reasons but none of them does so because an electron emits a photon.
 

Offline jccc

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Re: What is the difference between an electron and a photon?
« Reply #15 on: 17/07/2014 07:23:17 »
So the gas atom hit by the iron in Crook's tube got exited, the electrons bounded by the gas nucleus vibrate in quantum field to emit photon?

Is photon traveling in space or quantum field? After atoms emit photons, do they lose energy equals to e=mc^2?

Thanks Pete, I really should just study auto repair.

 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #16 on: 17/07/2014 12:26:23 »
Quote from: jccc
So the gas atom hit by the iron in Crook's tube got exited, the electrons bounded by the gas nucleus vibrate in quantum field to emit photon?
It's complicated how Crooke's tube works. Please read
http://en.wikipedia.org/wiki/Crookes_tube#How_a_Crookes_tube_works

Quote from: jccc
Is photon traveling in space or quantum field? After atoms emit photons, do they lose energy equals to e=mc^2?
Photons traveling space, not a quantum field. At least not as far as I know. And yes. They loose energy and thus they loose mass according to 281a70c20b16a38d7781189936e1ac9f.gif

Quote from: jccc
Thanks Pete, I really should just study auto repair.
Lol! You're welcome.
« Last Edit: 17/07/2014 12:29:54 by PmbPhy »
 

Offline dlorde

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Re: What is the difference between an electron and a photon?
« Reply #17 on: 17/07/2014 12:43:15 »
It's complicated how Crooke's tube works. Please read
http://en.wikipedia.org/wiki/Crookes_tube#How_a_Crookes_tube_works
Hmm, this article could cause some confusion - it says "When the electrons fall back to their original energy level, they emit light", and you have said "An electron cannot emit a photon", so on the face of it, the article you link to contradicts you.

Perhaps a more detailed or specific explanation would clarify...
 

Offline UltimateTheory

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Re: What is the difference between an electron and a photon?
« Reply #18 on: 17/07/2014 16:09:49 »
I just looked at the link to that photo. It's a Crooke's tube. You don't understand how it works and your misunderstanding of it has led you to use it to support your flawed idea that electrons emit photons.

Please go to the Wikipedia site and read how a Crook's tube works. You'll see that there is a difference of potential set up between the anode and cathode thus creating an electric field parallel to the axis of the cylinder of the tube. As ions (not electrons) accelerate along the tube's axis they collide with the atoms which make up the gas in the tube. When the atoms de-excite they emit photons.

How about you reading anything that is linked, or even provided by you??

Quote from Crookes tube description:
"When they strike it, they knock large numbers of electrons out of the surface of the metal, which in turn are repelled by the cathode and attracted to the anode or positive electrode."

Photons emitted by electrons are GREEN on right side of tube, right after cross.
Electrons are going from left to center, then bending path to bottom, and going to anode (positive electrode).

Electron must have ENOUGH kinetic energy to emit photons.
If it's going straight path, it usually must hit something to release its energy.
I am using it to create x-rays in my lab using > 40 kV and then observing ionization made by x-ray in Cloud Chambers..

If in electronic circuit there is U = 2.5 V, it means that each electron has kinetic energy E.K.=2.5 eV
That's why it won't emit f.e. UV photon by UV LED (Light Emitting Diode).

UV photon with 350 nm, needs U > 3.54 V.
UV photon with 400 nm, needs U > 3.1 V.

If kinetic energy of electron is smaller, photon won't be emitted and LED diode won't shine. Energy must be conserved.
« Last Edit: 19/07/2014 10:26:13 by CliffordK »
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #19 on: 17/07/2014 21:20:10 »
Quote from: UltimateTheory
Quote from Crookes tube description:
"When they strike it, they knock large numbers of electrons out of the surface of the metal, which in turn are repelled by the cathode and attracted to the anode or positive electrode."
So what?

Quote from: UltimateTheory
Photons emitted by electrons are GREEN on right side of tube, right after cross.
It's impossible for an electron to emit a photon. That's a well known fact that any particle physicist can tell you. Just read Griffiths text on particle physics and he'll explain it to you. For example, from Introduction to Elementary Particles by David Griffiths, page 59
Quote
The Feynman rules enforce conservation of energy and momentum at each vertex, and hence for the  diagram as a whole. It follows that the primitive QED vertex by itself does not represent a possible physical process. We can draw the diagram, but the calculation would assign to it the number zero. The reason is purely kinematical: 19f4104ecc82a7d0d374542cc009418e.gif would violate conservation of energy (In the center-of-mass frame the electron is initially at rest, so its energy is 2799d3215bc1b5dc7f4cdd1a8c7a044a.gif. It cannot decay into a photon plus a recoiling electron because the later alone would require an energy greater than 2799d3215bc1b5dc7f4cdd1a8c7a044a.gif.)
So there you have it. Straight "textbook physics" - An electron ".. cannot decay into a photon plus a recoiling electron ...".

<snipped more of his comments>
« Last Edit: 20/07/2014 06:07:08 by evan_au »
 

Offline UltimateTheory

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Re: What is the difference between an electron and a photon?
« Reply #20 on: 17/07/2014 22:06:02 »
In Crookes tube there is not "a single free electron in empty space".
There is beam of electrons, billions of electrons, and they interact with other electrons in beam, colliding each other.
There is electric field, that's not uniform (negative electrode on the left and positive electrode on the bottom).

Any answers in textbooks "can free electron emit photon?" are referring to situation about single particle and nothing else, no electric field, no magnetic field, no other forces, no collisions between multiple particles. Idealized situation in outer space.
« Last Edit: 17/07/2014 22:24:07 by UltimateTheory »
 

Offline PmbPhy

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Re: What is the difference between an electron and a photon?
« Reply #21 on: 19/07/2014 22:23:25 »
Quote from: UltimateTheory
In Crookes tube there is not "a single free electron in empty space".
Since electrons are point particles, one can zoom in and focus on individual particle/particle interactions. It's not as though electrons are all crammed together in space with no "elbow room".

Quote from: UltimateTheory
There is beam of electrons, billions of electrons, and they interact with other electrons in beam, colliding each other.
There is electric field, that's not uniform (negative electrode on the left and positive electrode on the bottom).

Any answers in textbooks "can free electron emit photon?" are referring to situation about single particle and nothing else, no electric field, no magnetic field, no other forces, no collisions between multiple particles. Idealized situation in outer space.
And still that doesn't mean that an electron can either absorb or emit a real photon. Even the text on particle physics by Griffiths, a highly respected author, is telling this. The only way for an electron to emit a photon is for either the electron or the photon (or was it both?) must be virtual particles. And they cannot be real particles and therefore they can't be observed. When I was talking to Griffiths about this he stressed to me that they're only used as mathematical tools and shouldn't be thought of as real objects. A virtual particle doesn't even lie on its mass shell. They have to go off-shell while in the Feynman diagram. They can't occur on a vertex which connects to outside the Feynman diagram.  They like inside the Feynman diagram. 

As Griffith writes
Quote from: David J. Griffiths
Also the Feynman rules enforce conservation of energy and momentum at each vertex, and hence for the diagram as a whole. It follows that the primitive QED vertex by itself does not represent a possible physical process.  We can draw the diagram, but calculation would assign to it the numberzero. The reason is purely kinematical; c1965b74adb3dfa3752211039e4edc58.gif.
I proved this mathematically in another post above.  So the only way that an electron can emit or absorb a photon is when the photon is a virtual particle at which point it can't be observed.
« Last Edit: 20/07/2014 06:03:03 by evan_au »
 

Offline UltimateTheory

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Re: What is the difference between an electron and a photon?
« Reply #22 on: 19/07/2014 22:46:51 »
I have devices like Crookes tube in the lab...

If you want to become a real scientist, I suggest you buying or building your own equipment..
http://www.ebay.com/sch/i.html?_nkw=crookes+tube
$70 is cost of Crookes tube + Cockcroft Walton generator producing 40 kV cost $30.
« Last Edit: 20/07/2014 05:58:29 by evan_au »
 

Offline UltimateTheory

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Re: What is the difference between an electron and a photon?
« Reply #23 on: 19/07/2014 23:35:28 »
If you want to see electrons, which loses their kinetic energy while passing through medium (and ionizing its molecules), build Cloud Chamber...

« Last Edit: 20/07/2014 05:54:31 by evan_au »
 

Offline Ethos_

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Re: What is the difference between an electron and a photon?
« Reply #24 on: 20/07/2014 01:29:52 »
Name calling will not advance our scientific knowledge one bit. It's a waste of time to deal with people that are only here to argue!
« Last Edit: 20/07/2014 05:53:28 by evan_au »
 

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Re: What is the difference between an electron and a photon?
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