Which of the following describes discrete radioactive particles?

• A. A cloud of radioactive material in air
• B. Contamination that exists as individual particles
• C. A uniform coating on a surface
• D. Contamination that cannot be measured by dpm or cpm

Answer: (B)

Discrete radioactive particles are contamination that exists as individual particles rather than as a continuous spread. This means you’d have separate specks or grains of radioactive material, each carrying activity. That’s why this description fits best: it captures the idea of distinct particles rather than a cloud or a uniform film. A cloud in the air describes airborne contamination, which isn’t made of separate particles in the same way. A uniform coating describes a surface contamination that is spread evenly rather than as discrete bits. And the idea that contamination cannot be measured by dpm or cpm isn’t correct—these units measure radioactive decay or counts and can quantify contamination when proper sampling and detectors are used, including for discrete particles.