Rad measures energy deposited or absorbed in what?

• A. Time of exposure
• B. Rate of disintegration
• C. Energy deposited/absorbed in a medium
• D. Exposure in air

Answer: (C)

Rad is a unit of absorbed dose, meaning it measures how much energy from ionizing radiation is deposited in a given mass of matter. It focuses on energy actually deposited per unit mass in the material (the medium), such as tissue. One rad corresponds to 0.01 joules of energy deposited per kilogram (0.01 Gy). This is different from exposure in air (which relates to ionization of air and has its own units) and from dose rate (energy per mass per time). So the rad specifically reflects energy deposited/absorbed in a medium.