What are the three fundamental radiation protection principles?

• A. Time, Distance, Shielding
• B. Time, Distance, Filtration
• C. Distance, Velocity, Shielding
• D. Dose, Distance, Shielding

Answer: (A)

The essential trio of radiation protection principles is Time, Distance, and Shielding. Limiting the time you spend near the source reduces the total dose you receive. The distance from the source matters because exposure follows the inverse square law—the farther you are, the dramatically lower your dose (doubling distance roughly quarters the exposure). Shielding uses appropriate barriers to attenuate the radiation before it reaches you, providing a physical block that lowers exposure.

In practice, these three work together to keep exposure as low as reasonably achievable. Shorten exposure time where possible, maximize distance whenever feasible, and use suitable shielding to intercept the beam. Filtration, velocity, or dose alone are not the fundamental principles guiding protection: filtration reduces beam energy and patient dose but isn’t one of the core protective principles; velocity isn’t relevant; and dose is the result you’re trying to limit, not a guiding principle.