The rem is an older non-SI unit; its modern SI equivalent is the sievert.

• A. True
• B. False
• C. It measures exposure
• D. It measures energy

Answer: (A)

The rem is an old unit used to express the biological effect of radiation, while the sievert is its modern SI counterpart for the same quantity. Since 1 sievert equals 100 rem, the rem has been superseded by the sievert in SI practice. Thus stating that the rem is an older non-SI unit and its modern SI equivalent is the sievert is true. In practical terms, you’ll often see values in milli- or micro-sieverts, or occasionally in millirem, with the relevant conversions: 1 rem = 0.01 sievert, and 1 Sv = 100 rem. The rem doesn’t measure exposure or energy directly; exposure (air ionization) is measured in units like the roentgen, and energy deposition is measured in grays.