Which term describes the energy imparted by ionizing radiation per unit mass of irradiated material?

• A. Absorbed dose
• B. Dose equivalent
• C. Exposure
• D. Activity

Answer: (A)

Absorbed dose is the energy imparted by ionizing radiation per unit mass of irradiated material. It measures how much energy the material actually absorbs from the radiation field, and its unit is the gray (Gy), where 1 Gy equals 1 joule per kilogram. This helps predict heating effects and potential biological damage in the tissue being irradiated.

Dose equivalent, by contrast, accounts for differences in biological impact by applying a radiation-weighting factor to the absorbed dose, giving a sense of the potential harm to living tissue. Exposure refers to the amount of ionization produced in air, not energy deposited in matter. Activity describes how quickly a radioactive substance decays, i.e., its decay rate, not energy deposition.