At what energies is photoelectric absorption primarily effective?

Photoelectric absorption is primarily effective at low energies, typically in the range of a few keV to about 100 keV. This phenomenon occurs when a photon interacts with an atom and transfers all its energy to an inner shell electron, resulting in the ejection of that electron from the atom. The probability of this interaction occurs because, at lower photon energies, the energy of the incoming photon is in line with the binding energy of the inner shell electrons, which makes it feasible for the photon to dislodge the electron effectively.

As the energy increases beyond this range, the likelihood of photoelectric absorption decreases and other interactions, such as Compton scattering, become more prevalent. Thus, at higher energies, the mechanics of photon interactions with matter shift, reducing the effectiveness of photoelectric absorption and favoring different processes altogether. This distinction is essential for understanding radiation safety and the interactions of different types of radiation with matter in various medical and research applications.