Which characteristic describes Alpha particles?

Alpha particles are characterized primarily by their inability to penetrate materials effectively, which aligns well with the correct response. They consist of two protons and two neutrons, making them relatively large and positively charged. Due to their size and charge, alpha particles interact with matter quite heavily and can be easily absorbed by even a few centimeters of air or the outer layer of human skin.

This characteristic makes them substantially less penetrating compared to beta particles or gamma rays, which can travel through various materials more easily. The description of their tendency to absorb quickly and not penetrate deeply is essential in understanding their behavior in different contexts, such as radiation safety and protection measures.

While alpha particles are indeed heavier than beta particles, the primary defining trait concerns their penetration capabilities, which makes the absorption property the focal point of their behavior. Additionally, they do not travel faster than light, as this is a fundamental limit based on the theory of relativity. Thus, the option correctly highlighting their poor penetration aligns with the standard understanding of alpha particle characteristics in radiation physics.