What does "internal exposure" mean?

"Internal exposure" refers specifically to the scenario where an individual is exposed to radioactive materials that have entered the body through ingestion, inhalation, or absorption. This type of exposure is distinct from external exposure, which comes from radiation sources located outside the body.

The reason option B is accurately associated with the definition of internal exposure is because it highlights the mechanism through which radioactive substances enter the body, thus allowing for the potential to cause biological harm from within. Once radioactive materials are inside, they can emit radiation as they decay, impacting internal organs and tissues directly.

In contrast, the other options describe different types of radiation exposure that do not involve the uptake of radioactive materials into the body. For example, external sources or medical treatments involve radiation acting from outside the body without internal involvement. Understanding the difference between internal and external exposure is critical in radiation safety and health physics, as it informs the approaches for monitoring, prevention, and treatment in cases of exposure.