The rem is used to compare biological effects of different radiations on humans.

• A. The energy deposited in tissue
• B. The rate of disintegration
• C. The mass of radioactive material
• D. The biological effect of different radiations on humans

Answer: (D)

The key idea is that different radiations cause different amounts of biological damage for the same energy deposited. The rem (dose equivalent) converts absorbed dose into a common scale that reflects this varying biological effectiveness. It does this by multiplying the absorbed dose by a radiation weighting factor that accounts for how damaging the specific type of radiation is to tissue. This lets you compare hazards from alpha, beta, gamma, and other radiations on a single scale. For example, alpha particles cause much more damage per unit energy than gamma rays, so a given energy deposit from alpha radiation yields a higher dose equivalent in rem. Energy deposited in tissue alone doesn’t capture this difference, and the rate of disintegration (activity) or the mass of radioactive material aren’t direct indicators of biological harm. That’s why rem is used to compare biological effects of different radiations on humans. (1 rem = 0.01 sievert in SI units.)