The energy imparted by ionizing radiation per unit mass of irradiated material is known as which quantity?

• A. Stray Radiation
• B. Absorbed Dose
• C. Dose Equivalent
• D. Exposure

Answer: (B)

Absorbed dose is the energy deposited by ionizing radiation per unit mass of irradiated material. It’s defined as energy imparted divided by mass, and its unit is the gray (Gy), where 1 Gy equals 1 joule per kilogram. This quantity directly describes how much energy is deposited in the tissue or material, regardless of radiation type or biological effect.

Exposure, in contrast, measures the amount of ionization in air and uses units like coulombs per kilogram (historically roentgen); it does not tell you how much energy was deposited in a specific material. Dose equivalent builds on absorbed dose by applying a radiation weighting factor to account for differences in biological impact, yielding units of sievert. Stray radiation is not a standard dose quantity.

So, the energy imparted per unit mass of irradiated material is best described by the absorbed dose.