American Society of Radiologic Technologist (ASRT) Practice Exam

The choice indicating 90° is correct because it corresponds to the principle of radiation safety in radiologic imaging. Scattered radiation behaves in predictable ways, primarily spreading out from the source of the radiation, which in this case is the x-ray tube during a mobile exam.

When a radiographer stands at a 90° angle — perpendicular to the primary beam of radiation — the intensity of scatter radiation received is minimized. This is based on the inverse square law, which states that the intensity of radiation decreases as the distance from the source increases, and it also relates to how scatter radiation disperses from the point of origin.

In contrast, standing at lesser angles, such as 15°, 30°, or 45°, positions the radiographer closer to the path that scatter might take, increasing the likelihood of exposure to scattered rays. As the angle decreases from 90°, the exposure to scattered radiation tends to increase. Therefore, standing at 90° optimally protects the radiographer from scattered radiation during a mobile exam.