National League for Nursing (NLN PAX) Practice Exam

A sheet of paper is capable of stopping alpha particles due to their relatively large mass and positive charge. Alpha particles consist of two protons and two neutrons, making them heavier than beta particles or gamma rays, and they have a limited range in air, generally only traveling a few centimeters before they lose energy and are absorbed by matter.

The nature of alpha particles allows them to interact more readily with materials, losing their energy quickly through ionization of the surrounding atoms. Because of this, a simple barrier like a sheet of paper is sufficient to effectively block alpha radiation from penetrating further.

In contrast, beta particles, being smaller and more penetrating, can pass through paper but would be stopped by denser materials. Gamma rays and X-rays are high-energy electromagnetic radiation and require much denser materials such as lead or concrete to attenuate their intensity significantly. Thus, the ability of a sheet of paper to stop alpha particles makes it a unique and accurate answer.