In which interaction does the incident photon lose up to one-third of its energy?

In which interaction does the incident photon lose up to one-third of its energy?

• A. Photoelectric interaction
• B. Classical interaction
• C. Compton interaction
• D. Photodisintegration interaction

Answer: (C)

This item tests how much energy a photon can transfer to matter during scattering. In Compton scattering, a photon collides with a (loosely bound or free) electron and transfers some of its energy to the electron while the photon is scattered with reduced energy. The amount of energy transferred depends on the scattering angle; the energy of the scattered photon is E' = E / [1 + (E/mc^2)(1 − cos θ)], so the energy given to the electron is ΔE = E − E'. The maximum transfer happens when the photon is backscattered (θ = 180°), and that maximum fraction is ΔE_max/E = 2α/(1 + 2α) with α = E/(mc^2). For photons with energies around hundreds of keV, this maximum transfer can approximate one-third of the incident energy. That behavior—partial energy loss with scattering and a possible maximum around one-third of the original energy—is characteristic of Compton scattering. Other interactions either absorb the photon completely (photoelectric effect), leave the photon energy essentially unchanged (elastic scattering), or involve nuclear processes at much higher energies (photodisintegration), so they don’t describe losing up to about one-third of the energy in the same way.

This item tests how much energy a photon can transfer to matter during scattering. In Compton scattering, a photon collides with a (loosely bound or free) electron and transfers some of its energy to the electron while the photon is scattered with reduced energy. The amount of energy transferred depends on the scattering angle; the energy of the scattered photon is E' = E / [1 + (E/mc^2)(1 − cos θ)], so the energy given to the electron is ΔE = E − E'. The maximum transfer happens when the photon is backscattered (θ = 180°), and that maximum fraction is ΔE_max/E = 2α/(1 + 2α) with α = E/(mc^2).

For photons with energies around hundreds of keV, this maximum transfer can approximate one-third of the incident energy. That behavior—partial energy loss with scattering and a possible maximum around one-third of the original energy—is characteristic of Compton scattering.

Other interactions either absorb the photon completely (photoelectric effect), leave the photon energy essentially unchanged (elastic scattering), or involve nuclear processes at much higher energies (photodisintegration), so they don’t describe losing up to about one-third of the energy in the same way.