What happens to the attenuation coefficient as photon energy increases?

As photon energy increases, the attenuation coefficient typically decreases. This phenomenon occurs because higher energy photons are more penetrating and have a lower likelihood of interacting with matter compared to lower energy photons.

When the photon energy is low, the chances for interactions such as photoelectric absorption increase, which contributes to a higher attenuation coefficient. As the energy increases, processes like Compton scattering become more significant, which tend to result in a reduction of the attenuation coefficient. Essentially, high-energy photons are better able to pass through materials without being absorbed or scattered, leading to a decrease in attenuation.

This relationship is fundamental in various applications, including diagnostic imaging and radiation therapy, where understanding the interaction of photons with tissues is crucial for optimizing image quality and reducing radiation dose.