In the context of X-ray interactions, the photoelectric effect results in?

• A. An inner shell electron remaining in place
• B. An inner shell electron being ejected
• C. A gamma photon emitted
• D. The nucleus absorbing the photon

Answer: (B)

In X-ray interactions, the photoelectric effect occurs when an incoming photon is completely absorbed by an atom, transferring all of its energy to an electron, usually from an inner shell. If the photon's energy exceeds the binding energy of that inner-shell electron, the electron is ejected from the atom as a photoelectron, leaving a vacancy that is often filled by a higher-shell electron. This filling can emit a characteristic X-ray photon or an Auger electron. The energy of the ejected photoelectron equals the photon energy minus the binding energy of the ejected electron. This process does not involve the nucleus and does not emit a gamma photon as part of the interaction. Therefore, the result is the ejection of an inner-shell electron.