What do counts per minute (cpm) measure?

Answer: B — The amount of radiation detected per minute

Counts per minute (cpm) is a measure used to quantify the amount of radiation that is detected over a one-minute interval. This unit is commonly utilized in radiation detection and nuclear instrumentation, where it helps to indicate the intensity of radioactive decay occurring in a sample or the surrounding environment. In practice, a Geiger counter or similar radiation detection device will record the number of ionizing events detected in that minute, translating those interactions into cpm. Thus, the measurement provides a direct correlation to the level of radiation being emitted. The other options, while they may relate to concepts in physics or chemistry, do not pertain to the specific measurement of cpm. For example, counting electrons in an atom does not have a direct relationship with radiation detection, the volume of gas released does not reflect radiation levels, and temperature readings do not quantify radioactivity. This makes the choice indicating the amount of radiation detected per minute the accurate interpretation of what counts per minute signifies in radiation monitoring.