Hello everyone. I have an understanding problem with the Optical theorem definition.(adsbygoogle = window.adsbygoogle || []).push({});

From Wikipedia :

"In physics, the optical theorem is a general law of wave scattering theory, which relates the forward scattering amplitude to the total cross section of the scatterer. It is usually written in the form:

[tex]\sigma _{tot}=\frac{4\pi}{k}Im f(0)[/tex]

where f(0) is the scattering amplitude with an angle of zero, that is, the amplitude of the wave scattered to the center of a distant screen. Because the optical theorem is derived using only conservation of energy, or in quantum mechanics from conservation of probability, the optical theorem is widely applicable and, in quantum mechanics, σtot includes both elastic and inelastic scattering. "

What does "f(0) is the scattering amplitude with an angle of zero, that is, the amplitude of the wave scattered to the center of a distant screen" exactly mean ? Are we talking about a head to head scattering ? Does angle zero mean there is no impact parameter ?

I do not understand the physical situation...any help is welcome !

Thanks a lot in advance,

Erwin

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# Optical theorem definition

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