Safety Registry Practice Test

The three cardinal principles of radiation safety are time, distance, and shielding. They’re the practical actions you take to keep exposure low: limit how long you’re near the source, maximize the distance between you and the source, and use appropriate shielding to absorb or block radiation. The inverse square law isn’t a cardinal principle itself; it’s a physical relationship that describes how radiation intensity drops with distance from a source—doubling the distance reduces exposure to one-quarter of its former value. This law helps explain why distance is so effective, but it’s not a directive you enact like the three cardinal principles. So the statement that the inverse square law is not a cardinal principle correctly identifies it as not one of the three cardinal safety practices.