What happens to the intensity of radiation when the source is moved farther from an object?

• A. Varies depending on kilovoltage and milliamperage
• B. Increases
• C. Remains the same
• D. Decreases

Answer: (D)

The main concept here is how distance affects radiation intensity through the inverse square relationship. The tube emits a fixed amount of energy for a given exposure setting, but as the source moves farther away, the beam spreads over a larger area. This geometric spreading makes the intensity at the object drop proportionally to the square of the distance: if you double the distance, the intensity becomes one quarter; if you triple it, one ninth, and so on. Kilovoltage and milliamperage determine how much energy is produced, but the distribution in space is governed by distance, so moving the source farther away decreases the intensity.