OHST Practice Exam

Lead is an effective shield for gamma rays due to its high density and atomic number, which allow it to attenuate gamma radiation more effectively than other materials. Gamma rays have very high penetration power, which makes them challenging to shield against. To effectively reduce their intensity, materials need both substantial density and a significant atomic number to interact with the gamma photons, resulting in scattering and absorption.

Lead's density means that a relatively thin layer can absorb or weaken a considerable amount of gamma radiation. When compared to the other materials listed, lead typically offers superior shielding capabilities. For instance, while cement and water can provide some reduction in gamma radiation, they are heavier and less effective on a per-thickness basis than lead. Sheet steel, while stronger than water, is not as dense as lead, making it less effective for gamma shielding.

Choosing lead as the shield material aligns with established practices in radiation protection, where lead is commonly utilized in situations that require the shielding of gamma rays, such as in medical facilities or nuclear applications.