Which type of radiation can be stopped by a piece of paper?

Alpha radiation is composed of heavy, positively charged particles that are relatively large compared to other forms of radiation. Due to their size and charge, alpha particles have a very limited ability to penetrate materials. In fact, they can be stopped by something as thin as a piece of paper or even the outer layer of human skin. This characteristic makes alpha radiation much less hazardous when outside the body; however, if alpha-emitting materials are ingested or inhaled, they can pose significant health risks.

In contrast, gamma rays and X-rays are forms of electromagnetic radiation that have much greater penetration power and require denser materials like lead or concrete to shield against them. Beta radiation, while more penetrating than alpha, is also less penetrating than gamma radiation but typically requires materials such as plastic or glass for adequate blocking.