Optical theorem

The optical theorem Bohr - Peierls - Placzek theorem or relationship called, brings in the scattering theory the imaginary part of the scattering amplitude to the total cross section in context:

• : Total cross section
• K: wave number
• : Scattering amplitude for scattering angles

The physical meaning of this theorem is the Teilchenstromerhaltung. The scattered fraction corresponds to the reduction of the incident wave.