Which of the following statements about alpha radiation is true?

Alpha radiation consists of helium nuclei, which are made up of two protons and two neutrons. Due to their relatively large mass and positive charge, alpha particles interact strongly with matter, resulting in limited penetration abilities.

The statement that alpha radiation is stopped by a few centimeters of air is accurate. When alpha particles encounter air, they quickly lose energy and are absorbed within just a short distance. This means that while they can be very harmful if ingested or inhaled, they cannot penetrate far in the environment around them.

The incorrect options highlight different characteristics of alpha radiation. For instance, the ability to penetrate thick concrete is characteristic of more penetrating types of radiation, such as gamma radiation, rather than alpha particles. Although alpha particles are charged, they are positively charged, contrasting with the statement suggesting they are negatively charged. Furthermore, alpha particles do not travel at the speed of light; rather, they move significantly slower due to their mass. All of these aspects clarify why the choice regarding their limited penetration capability in air is the correct understanding of alpha radiation.