Which statement best describes the photoelectric effect?

Which statement best describes the photoelectric effect?

• A. It occurs when a photon scatters off a nucleus
• B. It results in pair production
• C. It occurs primarily in the Compton region
• D. It occurs when a photon is absorbed by an atom causing ejection of a bound electron

Answer: (D)

The photoelectric effect is the emission of a bound electron from an atom when light with enough energy is absorbed. If the incoming photon’s energy exceeds the electron’s binding energy (work function), the atom takes up that energy and the electron is ejected; any extra energy becomes the electron’s kinetic energy. This is why the statement describing a photon absorbed by an atom causing ejection of a bound electron is the best description. It also highlights a key experimental observation: below the threshold energy, no electrons are emitted, and above threshold the emission can continue as light energy increases, with the kinetic energy of the ejected electron increasing as the photon energy increases. The other scenarios describe different interactions. Scattering off a nucleus is a different process (nuclear or Rutherford-type scattering), not the absorption and ejection seen in the photoelectric effect. Pair production involves creating an electron-positron pair and requires much higher photon energies. Compton scattering involves a photon scattering from a free or loosely bound electron, resulting in a change of the photon’s direction and energy rather than causing ejection by absorption.

The photoelectric effect is the emission of a bound electron from an atom when light with enough energy is absorbed. If the incoming photon’s energy exceeds the electron’s binding energy (work function), the atom takes up that energy and the electron is ejected; any extra energy becomes the electron’s kinetic energy. This is why the statement describing a photon absorbed by an atom causing ejection of a bound electron is the best description. It also highlights a key experimental observation: below the threshold energy, no electrons are emitted, and above threshold the emission can continue as light energy increases, with the kinetic energy of the ejected electron increasing as the photon energy increases.

The other scenarios describe different interactions. Scattering off a nucleus is a different process (nuclear or Rutherford-type scattering), not the absorption and ejection seen in the photoelectric effect. Pair production involves creating an electron-positron pair and requires much higher photon energies. Compton scattering involves a photon scattering from a free or loosely bound electron, resulting in a change of the photon’s direction and energy rather than causing ejection by absorption.