What is the definition of one rad in terms of energy absorbed per unit mass?

• A. Absorbed dose of 1 joule per kilogram
• B. Absorbed dose of 0.01 joule per gram
• C. Absorbed dose of 1 erg per gram
• D. Absorbed dose of 100 ergs per gram

Answer: (D)

Absorbed dose is energy deposited per unit mass. One rad equals 0.01 joules of energy deposited per kilogram of material. To express this per gram, take 0.01 J/kg and apply it to 1 g (which is 0.001 kg): E = 0.01 J/kg × 0.001 kg = 1 × 10^-5 J. Converting to ergs (1 J = 10^7 erg) gives 1 × 10^-5 J = 100 erg. Since this is energy per gram, the absorbed dose is 100 erg per gram. That’s why the correct interpretation is 1 rad = 100 erg per gram, aligning with the relationship that 1 Gy = 100 rad.