What is the equivalent measure for REM in the SI system?

The equivalent measure for REM in the SI system is the Sievert. REM, which stands for Roentgen Equivalent Man, is a traditional unit used in radiological protection to quantify the biological effect of ionizing radiation. The Sievert serves a similar purpose in the International System of Units (SI), representing the same concept of radiation dose that factors in the biological impact of the radiation on human tissue. In radiological safety and protection, it is crucial to use units that accurately reflect the potential health effects of radiation exposure, and the Sievert is designed for this purpose, making it the correct choice.

While Gray is a measure of absorbed dose (the amount of energy deposited in a material), it does not take into account the biological effect of the radiation on the human body, which is why it is not equivalent to REM. Rad is also a unit for measuring absorbed dose and, like Gray, is not a measure of equivalent dose, which is what REM and Sievert represent. Thus, the distinction lies in the use of Sievert to specifically quantify the relative biological effectiveness of different types of radiation, aligning with the intent of the REM.