Which of the following is the unit of absorbed dose?

• A. Gray (Gy)
• B. Sievert (Sv)
• C. Becquerel (Bq)
• D. Coulomb per Kilogram (C/kg)

Answer: (A)

The key idea is that absorbed dose measures how much energy from ionizing radiation is deposited in a mass of material per unit mass. The unit for this is the gray, defined as one joule of energy absorbed per kilogram of matter. That’s why gray is the correct unit for absorbed dose.

The other terms describe different quantities: the sievert accounts for biological effects and reflects weighting factors applied to the energy to estimate risk, not the actual energy deposited. Becquerel measures activity—the rate of radioactive decays—rather than energy deposited. Coulomb per kilogram represents exposure or air kerma, which relates to ionization in air, not the absorbed energy in a material.