What does 'Roentgen Equivalent Man' (REM) measure?

'Roentgen Equivalent Man' (REM) is specifically designed to quantify the biological effects of ionizing radiation on human tissue. It takes into account not just the energy deposited in the tissue, but also the type of radiation and its potential to cause harm. This measure is vital for understanding the risk of radiation exposure in terms of health effects, as different types of radiation (like alpha, beta, or gamma rays) can have varying degrees of biological impact, despite possibly delivering the same amount of energy.

In contrast, the other options address different aspects of radiation. For instance, while the type of radiation exposure is important, it is not what REM measures directly; instead, REM considers how that exposure translates into potential biological damage. Similarly, a unit of radioactive decay would relate to the amount of radioactive material and its transformation over time, not the biological impact. Lastly, the amount of radiation emitted refers to the measurement of radiation in terms of energy output, rather than its effect on biological systems, which is the core focus of REM. Thus, REM serves as a crucial metric in assessing occupational and environmental exposure risks related to radiation.