Optical theorem

[humanino]

"The imaginary part of the forward scattering amplitude is proprtional to the total cross section"
OK, so what is the link with Optics !? :confused: :uhh:

I am not sure I got the right forum, I just didn't know which would be better for that (stupid) question

[vanesch]

Well, it is Optical, because in Born and Wolf (the bible of optics), in the 7th edition I find on page 720:

"the rate at which the energy is removed from the incident plane wave by the processes of scattering and absorption is proportional to the imaginary part of the scattering amplitude for scattering in the forward direction."

They also give, in a footnote, a reference to an article describing the history of this theorem, R.G. Newton, Amer. J. Phys. 44(1976), 639.
I didn't check...

cheers,
Patrick.