The energy absorbed per unit mass from radiation exposure is known as what?

• A. Dose
• B. Dose rate
• C. Exposure
• D. Dose equivalent

Answer: (A)

Absorbed dose is the amount of energy deposited by ionizing radiation in a unit mass of tissue or material. It quantifies how much energy the tissue actually absorbs, which is what can cause biological effects. The standard unit is the gray (Gy), where 1 Gy equals 1 joule of energy absorbed per kilogram of material.

This differs from exposure, which measures ionization in air (historically in roentgens and related units) and does not directly reflect energy deposited in tissue. It also differs from dose rate, which is how fast that energy is delivered (dose per unit time) rather than the total energy per mass. And it differs from dose equivalent, which adjusts the absorbed dose by radiation type to estimate potential biological risk; absorbed dose is a pure energy-per-mass quantity, while dose equivalent incorporates factors for damage potential.