Which type of radiation is unable to penetrate skin and can be blocked by clothing?

Alpha particles are a type of radiation composed of two protons and two neutrons, making them relatively large compared to other forms of radiation. Due to their significant mass and positive charge, alpha particles have low penetration power. They can be easily stopped by a sheet of paper, clothing, or even the outer layer of the skin. This characteristic is critical in radiation safety, as exposure to alpha radiation is generally less risky if the source is outside the body, as it cannot penetrate the skin.

In contrast, beta particles, gamma rays, and X-rays possess greater penetration abilities. Beta particles can penetrate the skin and may require a layer of plastic or glass for adequate shielding, while gamma rays and X-rays are highly penetrating electromagnetic radiation that necessitates dense materials like lead or thick concrete for effective blocking. Understanding these differences helps in assessing the appropriate safety measures needed to protect against various types of radiation exposure.