The dose to the patient is directly related to which factor?

• A. The duration of the exposure
• B. The distance from the source
• C. The shielding used
• D. The color of the screen

Answer: (A)

Dose to the patient increases with exposure time because the x-ray tube is on longer, emitting more photons and delivering more energy to the tissues. In practice, dose is tied to mAs (tube current times exposure time), so keeping the current constant, increasing the time raises the photon fluence and the energy deposited — doing this linearly with time.

Distance plays a role in the opposite way: as you move farther away, dose drops according to the inverse square law. Shielding helps by absorbing photons before they reach the patient, reducing dose. The color of the screen has no effect on radiation exposure.