Which statement is not a characteristic of the three cardinal principles of radiation safety?

Which statement is not a characteristic of the three cardinal principles of radiation safety?

• A. Time is a cardinal principle
• B. Distance is a cardinal principle
• C. Shielding is a cardinal principle
• D. Inverse square law is not a cardinal principle

Answer: (D)

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.

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.