Which of the following describes absorbed dose?

The absorbed dose is defined as the amount of energy deposited in a material, typically biological tissue, by ionizing radiation per unit mass of the material. This relationship is expressed as energy per unit mass, which is crucial when evaluating the biological effects of radiation on tissues.

The reason why energy per mass is the correct description lies in its direct relevance to understanding how radiation interacts with matter. By measuring the energy deposited in a given mass, the absorbed dose gives insight into potential biological damage.

This concept is quantified in gray (Gy), where 1 gray equals 1 joule of energy absorbed per kilogram of tissue. Understanding the absorbed dose is essential in contexts such as radiation therapy, where it is vital to deliver a precise amount of radiation to effectively treat cancer while minimizing harm to surrounding healthy tissue.

The options describing energy per unit area, energy per time, and energy over a lifetime do not capture the critical aspect of relating the energy from radiation interactions specifically to the mass of the absorbing material, which is the essence of what the absorbed dose signifies.