Which interaction results in total absorption of the incident photon?

Which interaction results in total absorption of the incident photon?

• A. Compton scatter
• B. Photoelectric effect
• C. Pair production
• D. Transmission

Answer: (B)

The photoelectric effect involves the complete absorption of an incident photon by an atom, typically occurring within the context of radiographic imaging. In this interaction, a photon collides with an inner shell electron, transferring all its energy to that electron, which then is ejected from the atom. This results in the total absorption of the incoming photon, converting its energy into kinetic energy of the emitted electron. The significance of this interaction in radiography lies in its influence on image contrast. The photoelectric effect is more likely to occur with photons that have energies slightly above the binding energy of the electron, particularly in denser tissues or materials that have a high atomic number. Thus, because the incident photon is fully absorbed, the photoelectric effect contributes to creating areas of high contrast in the resulting radiographic image, distinguishing different tissues based on their atomic composition. In contrast, other interactions such as Compton scatter involve partial energy transfer where the photon is deflected, and only part of its energy is absorbed by an outer shell electron, leading to scattering rather than complete absorption. Pair production is a different phenomenon that only occurs at high photon energies, where the photon transforms into an electron-positron pair, but it still does not involve total absorption in the same manner

The photoelectric effect involves the complete absorption of an incident photon by an atom, typically occurring within the context of radiographic imaging. In this interaction, a photon collides with an inner shell electron, transferring all its energy to that electron, which then is ejected from the atom. This results in the total absorption of the incoming photon, converting its energy into kinetic energy of the emitted electron.

The significance of this interaction in radiography lies in its influence on image contrast. The photoelectric effect is more likely to occur with photons that have energies slightly above the binding energy of the electron, particularly in denser tissues or materials that have a high atomic number. Thus, because the incident photon is fully absorbed, the photoelectric effect contributes to creating areas of high contrast in the resulting radiographic image, distinguishing different tissues based on their atomic composition.

In contrast, other interactions such as Compton scatter involve partial energy transfer where the photon is deflected, and only part of its energy is absorbed by an outer shell electron, leading to scattering rather than complete absorption. Pair production is a different phenomenon that only occurs at high photon energies, where the photon transforms into an electron-positron pair, but it still does not involve total absorption in the same manner