What unit is used to measure the amount of radiation received in terms of heat energy?

• A. Gray (Gy)
• B. MilliSievert (mSv)
• C. Radiation Absorbed Dose (RAD)
• D. Roentgen (R)

Answer: (C)

The Radiation Absorbed Dose (RAD) is the correct answer because it specifically measures the absorbed dose of radiation in terms of energy deposited in a material, particularly biological tissue. One RAD corresponds to an absorption of 0.01 joules of radiation energy per kilogram of matter. This makes it a direct measure of the amount of radiation that heats or energizes the tissue or material it interacts with, linking it to heat energy.

In this context, while the other units listed (Gray, MilliSievert, and Roentgen) are also used in different ways to measure and quantify radiation exposure, they serve different purposes. The Gray is a more modern unit and has a direct relationship with the RAD, where 1 Gy is equal to 100 RAD, and it likewise measures absorbed dose. However, the RAD is historically used and often referenced in contexts related to thermal energy absorption. The MilliSievert is a unit used for measuring the biological effect of radiation, not temperature or heat energy, while the Roentgen measures exposure in the air and is less relevant to the concept of heat energy absorption in tissues.