# Talk:Thomson scattering

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### Redirect

Electron scattering redirects to this page, but this must be a mistake? In my opinion, "Electron scattering" refers to the scattering of electrons (for example by atoms), not scattering _by_ electrons. If no-one objects, I'll remove the redirect and just write a small stub article on "Electron scattering". O. Prytz 22:58, 30 December 2005 (UTC)

Done O. Prytz 10:52, 31 December 2005 (UTC)

### Compton Scattering

I found it surprising that there's no mention of Compton scattering on this page, even though the only difference seems to be whether or not the electron absorbs energy from the incident photon. I can't really think where to fit it in though... Warrickball (talk) 14:03, 11 May 2008 (UTC)

## Downplayed CGS units

The equation for the Thomson differential cross section was given as

${\displaystyle {\frac {d\sigma _{t}}{d\Omega }}\equiv \left({\frac {q^{2}}{mc^{2}}}\right)^{2}{\frac {1+\cos ^{2}\chi }{2}}=\left({\frac {q^{2}}{4\pi \epsilon _{0}mc^{2}}}\right)^{2}{\frac {1+\cos ^{2}\chi }{2}}}$

The use of SI and CGS units in the same equation is extremely confusing. It's like placing an egg in your handbag -- it's okay for a few minutes if you're careful, but if you leave it for long you're likely to forget the setup and make a mistake.

To remedy this, I removed the CGS units (leaving just a mention in the text).

Is this right? Or is there a "segue" from CGS to SI that occurs at this point in the text -- that I missed through inexperience-- and that I have now obscured?

84.226.185.221 (talk) 13:08, 12 October 2015 (UTC)

## Something is wrong with the Thomson differential cross section

I don't understand how:

(1) At first, we treat σt as a constant to be carried along while integrating over the sphere. It gets multiplied by a factor of 1+cos2χ coming from the emissivity coefficients εr and εt.

(2) But then, we obtain σt itself by integrating a non-constant density dσt/dΩ over the sphere. The non-constant density contains an internal factor of 1+cos2χ.

Is the factor of 1+cos2χ supposed to be incorporated in σt, or not?

What is the exact relation between the Thomson differential cross section dσt/dΩ and the emissivity coefficients εr and εt?

It seems as if this derivation was constructed from two partial, slightly disparate versions, perhaps from two different sources, but laid on top of each other and not fully integrated.

84.226.185.221 (talk) 13:08, 12 October 2015 (UTC)