What is the most useful way to measure radiation exposure?

• A. Counts per minute
• B. mRems/hour
• C. Sieverts per hour
• D. Roentgens per hour

Answer: (B)

The key idea is to measure exposure in terms of the dose that actually affects the body, not just the detector reading or the air. Counts per minute only tells you how many particles the detector sees, not how much energy is deposited in tissue. Roentgens per hour indicates ionization in air, which doesn’t directly translate to the amount of radiation energy absorbed by a person. What matters for health risk is the dose equivalent rate, which accounts for the type of radiation and how it affects tissue. That makes millirem per hour (or, in SI terms, millisieverts per hour) the most useful way to express exposure for protective decisions. While sieverts per hour would be conceptually correct, millirem per hour is the commonly used practical unit in many field and health-protection contexts, aligning with risk assessments and action levels.