Do electrons radiate from electostatic acceleration?

[Lazarus]

Does an electron radiate while being accelerated by an electrostatic force or gravitational force?

 

The posts here say it always radiates when accelerated. It has been demonstrated that electromagnetic force causes the electron to radiate.

 

Is there an experiment that determines the result of electrostatic force?

 

This item on the internet seems to contend that acceleration doesn’t always cause the electron to accelerate.

 

Will the real answer please stand up? (You aren’t old enough to remember that show.)

 

The physics Hypertxtbook

1998-2013 Glenn Elert

 

X-rays are produced whenever fast moving electrons are decelerated, not just in x-ray tubes. Nearly all the naturally occurring x-ray sources are extraterrestrial. (No, that doesn't mean produced by alien creatures from outer space. It just means ''beyond the earth”). X-rays are produced when the solar wind is tapped by the earth's magnetic field in the Van Allen Radiation Belts. Black holes are significant sources of x-rays in be universe. Matter falling into a black hole experiences extreme acceleration caused by the intense field of the black hole.

 

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A single isolated particle would fall in without releasing any radiation, but a stream of particles would, as the particles would wind up crashing into each other on their way down the hole.

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Each inelastic collision experienced by a charged particle would result in the emission of a photon. Since these collisions are taking place at great speeds. the energies of the emitted photons are on the order of those found in the x-ray region of me electromagnetic spectrum. Inelastic collisions at even higher energies (greater than a million electron volts) would generate gamma rays.

 

[Enthalpy]

Nice of you to take care of presbyopic readers, but I wear my glasses, thanks.

 

You answered it: quick electrons radiate in the electrostatic field of a nucleus.

[swansont]

Does an electron radiate while being accelerated by an electrostatic force or gravitational force?

 

 

A single isolated particle would fall in without releasing any radiation,

 

 

Yes. Why wouldn't a single particle radiate?

[Lazarus]

Swansont said:

Yes. Why wouldn't a single particle radiate?

 

 

Reply:

 

The electron in a synchrotron is accelerated by magnetic forces and it radiates.

That doesn't necessarily mean that electrostatic acceleration should radiate.

 

Do the electrons traveling towards the screen in a TV radiate on the way?

[Sensei]

Do the electrons traveling towards the screen in a TV radiate on the way?

 

 

Crookes tube:

http://en.wikipedia.org/wiki/Crookes_tube

 

Inside this tube type there is very small amount of gas.

 

We can see electrons path, because they emitted photons.

 

 

 

When gas is present in the path of electrons, glow discharge is happening

http://en.wikipedia.org/wiki/Glow_discharge

 

It's used in discharge tubes:

http://en.wikipedia.org/wiki/Gas-filled_tube

 

[swansont]

 

The electron in a synchrotron is accelerated by magnetic forces and it radiates.

That doesn't necessarily mean that electrostatic acceleration should radiate.

 

Do the electrons traveling towards the screen in a TV radiate on the way?

 

Electrons traveling toward a screen are not accelerating. The acceleration occurs between the plates held at a potential difference. And the electrons would radiate during that acceleration.

 

Crookes tube:

http://en.wikipedia.org/wiki/Crookes_tube

 

Inside this tube type there is very small amount of gas.

 

We can see electrons path, because they emitted photons.

 

 

 

 

When gas is present in the path of electrons, glow discharge is happening

http://en.wikipedia.org/wiki/Glow_discharge

 

It's used in discharge tubes:

http://en.wikipedia.org/wiki/Gas-filled_tube

 

 

 

Glow discharge is from ionization, not bremsstrahlung.

[Sensei]

Yes I know. But after molecule has been ionized it must intercepting electron from environment to become neutral again, so some electron must emit photon to do so.

[Lazarus]

Please point me to an experiment or apparatus that demonstrates the radiation.

[swansont]

Please point me to an experiment or apparatus that demonstrates the radiation.

Electrons slamming into a piece of metal experience electrostatic forces that bring them to a stop and cause them to emit radiation. It's called bremsstrahlung, and you can make x-rays this way. I've observed it dozens of times myself when I was a TA; it is a standard physics lab experiment.

[Strange]

Please point me to an experiment or apparatus that demonstrates the radiation.

 

Some examples here: http://hyperphysics.phy-astr.gsu.edu/hbase/particles/synchrotron.html

[Sensei]

Please point me to an experiment or apparatus that demonstrates the radiation.

 

Crookes tube, that I showed above in #5 post, with metal plate on the path of electrons, with enough high voltage, will produce x-rays.

Edited December 24, 2013 by Sensei

[Enthalpy]

Electrons continue to accelerate all the way to the screen in a cathode ray tube: the electron gun uses just a few 100V over 20kV. The electrons must emit a bit on the way, but this is a limited voltage over a long time. Significant emission is rather with 100keV+ energy and deviation over 1pm, and even better if the electron moves toward the observer at nearly c.

 

Also, as the electron throughput is random, their emission is uncorrelated and adds poorly. As opposed, a free electron laser has its electrons organized in bunches that combine well with the successive magnets.

[Sensei]

You need electron gun- two plates of metal, one with hole with + charge on it, and one solid with - charge (that's where electrons will gather).

To plates there is connected high voltage. Normally electrons would move between plates.

But when we will add magnets/electromagnets to bend electron beam, they will fly through hole in + metal plate, and will continue moving in vacuum.

 

Everything in high vacuum, to minimize chance to ionize gas atoms.

 

Then electrons can hit some medium that we will place on its path, such as metal plate.

When voltage is enough x-rays will be produced.

 

[Lazarus]

swansont said:

Electrons slamming into a piece of metal experience electrostatic forces that bring them to a stop and cause them to emit radiation. It's called bremsstrahlung, and you can make x-rays this way. I've observed it dozens of times myself

 

Reply:

When electrons lose kinetic energy it is certainly reasonable that they would radiate.

 

An electron colliding with something could lose kinetic energy and thus radiate. That doesn't seem to demonstate that electrostatic force is the cause of the radiation.

 

Strange said:

Some examples here: http://hyperphysics....ynchrotron.html

 

Reply:

Thank you for the information. There seems to be magnetic forces involved so it is not clear what the role of the electrostaicforces is.

[Strange]

There seems to be magnetic forces involved so it is not clear what the role of the electrostaicforces is.

 

Magnetism and electrostatic forces are the same thing (clue: it is called electromagnetic force for a reason) so I don't see why it would make any difference. It is the acceleration that is important not the force causing it.

Edited December 24, 2013 by Strange

[Lazarus]

Strange said:

Magnetism and electrostatic forces are the same thing (clue: it is called electromagnetic force for a reason) so I don't see why it would make any difference. It is the acceleration that is important not the force causing it.

 

Reply:

There are different rules for electromagnetic forces from electrostatic forces so how can they be the same thing?

[swansont]

Strange said:

 

There are different rules for electromagnetic forces from electrostatic forces so how can they be the same thing?

they change from one to another when you change reference frames. They are different manifestations of the phenomenon.

swansont said:

 

When electrons lose kinetic energy it is certainly reasonable that they would radiate.

 

An electron colliding with something could lose kinetic energy and thus radiate. That doesn't seem to demonstate that electrostatic force is the cause of the radiation.

 

 

Electrostatic forces can cause accelerations, thus they can change the KE and cause the charge to radiate.

Electrons continue to accelerate all the way to the screen in a cathode ray tube

Typically the accelerating potential hardware is located in the back, before it widens.

[Lazarus]

The logic is sound that an electron should radiate when is loses kinetic energy by slowing down. Even in a synchrotron the electron slows down when turning a corner. That should be true for andelectron being slowed by electrostatic force.

 

If the electron is being accelerated by electrostatic or gravitational forces it may not follow that is has to radiate.

 

There have to be experiments accelerating electrons through a high voltage difference that would show the radiation. That is what i would like to know.

 

Thanks for your patience with me.

[swansont]

The logic is sound that an electron should radiate when is loses kinetic energy by slowing down. Even in a synchrotron the electron slows down when turning a corner. That should be true for andelectron being slowed by electrostatic force.

 

If the electron is being accelerated by electrostatic or gravitational forces it may not follow that is has to radiate.

 

There have to be experiments accelerating electrons through a high voltage difference that would show the radiation. That is what i would like to know.

 

Thanks for your patience with me.

Electrons slow down in a material due to the electrostatic force, and they radiate as a result. The acceleration is not somehow separate from the electrostatic force.

[Lazarus]

The distinction is that slowing down means the electron has less kinetic energy. Speeding up means it has more kinetic energy.

Less energy I understand has to be compensated for. For the electron to have more kinetic energy shouldn't require dissipation of energy by releasing a photon.

[swansont]

Why would a magnetic acceleration cause radiation, then? Magnetic forces don't change KE.

[Lazarus]

#21 swansont

Posted Today, 02:54 AM

Why would a magnetic acceleration cause radiation, then? Magnetic forces don't change KE.

Reply:

But you said that the electron loses energy and slows down in the magnetic turning field in the synchrotron.

[swansont]

 

#21 swansont

Posted Today, 02:54 AM

Why would a magnetic acceleration cause radiation, then? Magnetic forces don't change KE.

Reply:

But you said that the electron loses energy and slows down in the magnetic turning field in the synchrotron.

 

 

That's because of the radiation, not because the magnetic force does any work. Magnetic forces are perpendicular to the velocity. They don't change the KE.

[Lazarus]

Merry Christmas

 

What you say is completely reasonable.

 

It's the chicken and egg problem that conserns me. Is the electron slowed because it radiated or did it radiate because is slowed?

 

A spark from across an open contact doesn't help because of the air in the way. An antenna doesn't fit because the electrons don't have time to travel the length of the antenna and also collide with atoms.

 

To demonstrate the difference all you need to do is pull out your electron gun and shoot at a highly positive target through a vacuum and you should be able to see the path of the electrons.

 

The case for electrons "always" radiating when their velocity vector changes is strong but so far not bulletproof. It is testable and certainly that has been done.

[imatfaal]

Merry Christmas

 

What you say is completely reasonable.

 

It's the chicken and egg problem that conserns me. Is the electron slowed because it radiated or did it radiate because is slowed?

 

 

 

A magnetic field always acts perpendicular to the direction of motion - it is thus impossible for it to do work on the particle and thus impossible for it to slow the particle's forward motion down. However it can accelerate the particle in a perpendicular direction (ie around a circle) - this acceleration will cause the particle to radiate.

 

It cannot be that the electron radiates because it was slowed - as a perpendicular force cannot slow it down