Radiation Safety Practice Exam

Which radiation measurement unit is the smallest?

1. Gy

2. Sv

3. REM

4. Bq

The correct answer is: Bq

The correct answer, which identifies the smallest radiation measurement unit, is the Becquerel (Bq). The Becquerel is a unit that measures the activity of a radioactive substance, indicating the number of disintegrations or transformations that occur per second, specifically one disintegration per second. Since it quantifies the rate at which radioactive decay happens, it is an appropriate measure when considering small amounts of radiation emission. In contrast, the other units—Gray (Gy), Sievert (Sv), and roentgen equivalent man (REM)—serve different functions in radiation measurement. The Gray measures absorbed dose, indicating the amount of radiation energy deposited in a given mass of material, often tissues in biological contexts, and is larger in terms of the quantity measured. The Sievert and REM both measure biological effect and dose equivalency, accounting for the type of radiation and its impact on human health, also representing much larger quantities. Therefore, when comparing these units, the Becquerel stands out as the smallest, being focused on activity rather than dose or effect.