The intensity of the scattered beam is 1/1000 the intensity of the primary beam at a ________ angle 1 m from the patient.

• A. 45-degree
• B. 25-degree
• C. 90-degree
• D. 10-degree

Answer: (A)

Scattered radiation around a patient is not uniform; its intensity depends on the angle relative to the incident beam. At a distance of about 1 meter, a practical rule of thumb used in shielding and safety is that the scattered photons reaching you at mid-angles are about one thousandth of the primary beam. That mid‑angle is around 45 degrees from the beam, which is why this value is given here. The idea is to reflect a representative amount of scatter you might encounter at typical work positions: at angles closer to the beam (forward directions) the scatter is smaller, while at angles near 90 degrees (perpendicular to the beam) the scatter increases. So 45 degrees serves as a convenient reference point for estimating scatter intensity at 1 meter.