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Electrons and Photons?

Under the right circumstance in a synchrotron for example, electrons accelerated to very high speeds can be made to give off photons. Apparently to preserve the laws of conservation of momentum and conservation of energy.


i assume this means the photons in this case have mass to allow the electron to obey these laws so does this mean:

1. Electrons contain the photons
2. Electrons generate the photons
3. Photons are spontaneously generated by some other effect
4. The electrons are dragging photons along with them.

Why do i have a feeling I am not going to understand the answer, if I could I probably wouldn't have asked the question!

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kelseymh5 years ago
Synchrotron radiation can be understood conceptually as a purely classicial effect; it's not a conservation issue per se, and doesn't even need quantum mechanics to understand. When a charged particle is accelerated (i.e., when a force is applied to change its momentum), that particle will radiate EM.

Non-relativistically, this is the Larmor effect, which is the exact same effect which produces radio waves in an antenna!

For charged particles moving relativistically (i.e., close to the speed of light), the Larmor formula has to be modified somewhat to be correct. You can follow links from the article above to find those details.

Now, on to your questions.

0) Free, radiated photons do not have mass. They propagate in vacuum at the speed of light.

1) Nope. The "photons" (EM radiation) are generated by the accelerated charge.

2) Yup. See above.

3) Not sure what you mean by "spontaneously" here.

4) Electrons, which have a charge, are always "dragging photons" along with them, since photons are the quanta of the electromagnetic field.
rickharris (author)  kelseymh5 years ago
Thank you for that I will look up the lnks
frollard5 years ago
in order for the electron to give off a photo it has to hit something, release some of its kinetic energy, and the dropping energy level of that ionized thing will give off a photo.

I could be wrong, but electron guns/accelerators don't give off photos per se.

Electrons do indeed have mass, hence why they cannot exceed c.

A photon is a quanta of energy - you can take energy from a kinetic electron and MAKE a photon.
rickharris (author)  frollard5 years ago
reason for the question - I can across this dipping into youtube.

:-(
rickharris (author)  iceng5 years ago
See this is how they do science in the UK - Who said our schools were dumbing down?
Scary thing is a good voice is as convincing as a politician