What is a measure of any type of radiation expressed in terms of its estimated biological effects?

• A. Rem
• B. Sievert
• C. Rad
• D. Curie

Answer: (A)

The main idea here is dose equivalent—the amount of radiation evaluated by its potential biological effects, not just how much energy is deposited. This concept recognizes that different types of radiation cause different levels of harm, so a weighting factor is applied to reflect that harm.

The unit rem is the traditional measure of dose equivalent. It expresses how much biological effect a given radiation exposure is likely to cause, by incorporating those weighting factors. The absorbed dose (rad) measures energy deposited per mass, but it doesn’t account for how damaging the radiation type is. Curie represents activity (how many decays per second), not biological effect. The modern SI unit for dose equivalent is the sievert, where 1 sievert equals 100 rem.

So, rem is the best match for a measure that expresses estimated biological effects, with sievert serving as the modern equivalent.