Question

When a photon interacts with an orbital electron of an atom in compton scatering some of the photons energy is transfred to the electron as kinetic energy and the rest of the energy leaves as a new photon. Is Egamma1 = Telectron + binding energy of the electron + Egamma 2 the energy conservation equation? Im just confused by the fact that textbooks say that the energy of the original gamma is equal to the kinetic energy of the ejected electron plus the energy of the new gamma. Doesnt some energy get used up in ejecting the electron?

Answer 1

Main thing about Compton effect is, it is performed by usually X-rays ( or gamma rays). The energy of the X- rays are in order of MeV ( even for soft X- rays it is of order of 5 - 10 kev). In case of atoms, the binding energies of the electrons are of order of eV, like Hydrogen, only 13.6 eV. So, for incoming X-ray photon it is considered that electrons are free, that is, not binded. Because energy used by X-Ray photon to eject a electron from an atom is too much low than its energy. So, usually electron's binding energy is neglected. If sharp calculations are being done, then it is good to consider the binding energy of the electron according to energy conservation. ( Gamma rays have higher energy than X-rays)