Which principle involves keeping distance from the radiation source as far as possible?

• A. Time
• B. Shielding
• C. Distance
• D. Bucky tray

Answer: (C)

The principle being tested is reducing radiation exposure by increasing distance from the source. This relies on the inverse square relationship: as distance doubles, the dose becomes about one-quarter; tripling distance reduces it to roughly one-ninth, and so on. Because of this, keeping as much space as possible between you and the radiation source significantly lowers your exposure, often more effectively than other single adjustments.

In practice, this means stepping back during imaging, using remote controls to operate equipment, and having others leave the room when an exposure occurs. Time and shielding are also important controls, but the question focuses on the distance aspect. The Bucky tray is a device for supporting the image receptor and does not by itself govern exposure through distance.