Some questions about photons and electrons

[swansont]

Would the electron repel the photon as if it had the same charge? And is it impossible for free electrons to absorb photons?

 

No. There's nothing like electrostatic repulsion going on.

 

Free electrons can't absorb photons. Either energy or momentum would not be conserved; it's a nice little exercise for those learning this level of physics to show this.

[Sato]

No. There's nothing like electrostatic repulsion going on.

 

Free electrons can't absorb photons. Either energy or momentum would not be conserved; it's a nice little exercise for those learning this level of physics to show this.

 

Oh okay, unfortunately I do not think I am at that level yet.

If it's not like that, then what causes the photon to scatter away from the electron?

[swansont]

Oh okay, unfortunately I do not think I am at that level yet.

If it's not like that, then what causes the photon to scatter away from the electron?

 

Photons interact electromagnetically, and electrons do as well.

[Sato]

Photons interact electromagnetically, and electrons do as well.

 

Oh okay, and it's a concrete law of electromagnetism that unbound electrons will repel photons?

[swansont]

Oh okay, and it's a concrete law of electromagnetism that unbound electrons will repel photons?

 

Repel is not a word I would use, because this does not take place like electrostatic repulsion, which varies with distance (1/r^2). Electrons scatter photons. Compton scattering happens http://en.wikipedia.org/wiki/Compton_scattering

[Sato]

Repel is not a word I would use, because this does not take place like electrostatic repulsion, which varies with distance (1/r^2). Electrons scatter photons. Compton scattering happens http://en.wikipedia.org/wiki/Compton_scattering

 

I have read through that article as well as others on the topic of scattering theory but my comprehension rate was not very high, I think due to the concentration of jargon on the wikis. How would you describe it?

[swansont]

I have read through that article as well as others on the topic of scattering theory but my comprehension rate was not very high, I think due to the concentration of jargon on the wikis. How would you describe it?

 

The photon scatters off of the electron. In this case it's not that different from marbles colliding. But since there's a photon, its energy change shows up as a wavelength change, and it depends on the scattering angle.

 

If you're not at the level where you can show how the scattering violates absorption would violate conservation of energy or momentum, it's really hard to have any substantive discussion.

[Sato]

The photon scatters off of the electron. In this case it's not that different from marbles colliding. But since there's a photon, its energy change shows up as a wavelength change, and it depends on the scattering angle.

 

If you're not at the level where you can show how the scattering violates conservation of energy or momentum, it's really hard to have any substantive discussion.

 

Oh okay, I understand. Thank you for your help!

[ACG52]

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If you're not at the level where you can show how the scattering violates conservation of energy or momentum, it's really hard to have any substantive discussion.

Did you mean doesn't violate conservation of energy or momentum?

[swansont]

.

Did you mean doesn't violate conservation of energy or momentum?

 

 

Good catch, I meant absorption. Fixed.