Which of the following is NOT a characteristic of alpha particles?

• A. Can be stopped by paper
• B. Have a positive charge
• C. Are highly penetrating
• D. Are heavy particles

Answer: (C)

Alpha particles are composed of two protons and two neutrons, making them relatively heavy compared to other forms of radiation, such as beta particles or gamma rays. They carry a positive charge due to the presence of protons. One of the most notable characteristics of alpha particles is their low penetration capability; they can be effectively stopped by very thin materials, such as a sheet of paper or the outer layer of human skin.

The assertion that alpha particles are highly penetrating contradicts their actual behavior. Unlike beta particles or gamma rays, which can penetrate more deeply into materials, alpha particles are unable to pass through anything more substantial than a few centimeters of air or a piece of paper. Therefore, this characteristic is not true, confirming that alpha particles do not possess high penetration ability.