Which term describes elastic scattering of photons in radiography?

Which term describes elastic scattering of photons in radiography?

• A. Compton scatter
• B. Photoelectric effect
• C. Pair production
• D. Coherent (classical) scatter

Answer: (D)

Elastic scattering of photons by atoms means the photon changes direction without losing energy, a process known as coherent scatter (Rayleigh scattering). This is the elastic interaction radiographic photons can undergo, where virtually no energy is transferred to the atom and no ionization occurs. Among the options, this is the elastic scattering term. Compton scatter, in contrast, is inelastic: the photon loses energy to a recoil electron, changing the photon’s energy and giving energy to the atom. The photoelectric effect is absorption, where the photon is taken up and an inner-shell electron is ejected. Pair production requires photon energy above 1.022 MeV and results in an electron-positron pair, not a simple scattering event. So the term describing elastic scattering of photons in radiography is coherent (classical) scatter.

Elastic scattering of photons by atoms means the photon changes direction without losing energy, a process known as coherent scatter (Rayleigh scattering). This is the elastic interaction radiographic photons can undergo, where virtually no energy is transferred to the atom and no ionization occurs. Among the options, this is the elastic scattering term. Compton scatter, in contrast, is inelastic: the photon loses energy to a recoil electron, changing the photon’s energy and giving energy to the atom. The photoelectric effect is absorption, where the photon is taken up and an inner-shell electron is ejected. Pair production requires photon energy above 1.022 MeV and results in an electron-positron pair, not a simple scattering event. So the term describing elastic scattering of photons in radiography is coherent (classical) scatter.