Which interaction results in production of a photoelectron that is ejected from the atom?

Which interaction results in production of a photoelectron that is ejected from the atom?

• A. Photoelectric interaction
• B. Compton interaction
• C. Coherent scatter
• D. Pair production

Answer: (A)

The main idea here is the photoelectric effect: a photon is completely absorbed by an atomic electron, typically a tightly bound inner-shell electron, and the excess energy becomes the kinetic energy of the ejected photoelectron. This absorption leaves a vacancy in the atom, which can be filled later by electrons from higher shells, sometimes emitting characteristic X-rays or Auger electrons. The key point is that the photon is fully absorbed and the ejected particle is specifically a photoelectron. In the other interactions, no photoelectron is produced in this sense. Compton scattering involves only partial energy transfer to an electron and a scattered photon remains, so the ejected electron is not a photoelectron. Coherent (Rayleigh) scattering transfers energy with no ionization, so no electron is ejected. Pair production creates an electron-positron pair from the photon’s energy in the presence of a nucleus, not a single bound-electron ejection.

The main idea here is the photoelectric effect: a photon is completely absorbed by an atomic electron, typically a tightly bound inner-shell electron, and the excess energy becomes the kinetic energy of the ejected photoelectron. This absorption leaves a vacancy in the atom, which can be filled later by electrons from higher shells, sometimes emitting characteristic X-rays or Auger electrons. The key point is that the photon is fully absorbed and the ejected particle is specifically a photoelectron.

In the other interactions, no photoelectron is produced in this sense. Compton scattering involves only partial energy transfer to an electron and a scattered photon remains, so the ejected electron is not a photoelectron. Coherent (Rayleigh) scattering transfers energy with no ionization, so no electron is ejected. Pair production creates an electron-positron pair from the photon’s energy in the presence of a nucleus, not a single bound-electron ejection.