What type of radiation can be stopped by the skin?

Alpha radiation is composed of heavy, positively charged particles that originate from the nucleus of an atom. These particles are relatively large and have a low penetration ability. As a result, they can be stopped by the outer layer of human skin, making alpha radiation less harmful when the source is external to the body. However, if alpha-emitting materials are ingested or inhaled, they can pose significant health risks due to their high ionizing power.

In contrast, beta radiation, while it has greater penetration ability than alpha particles, can still be absorbed by materials like plastic or aluminum, but it can penetrate the skin to some extent. Gamma radiation and X-ray radiation are forms of electromagnetic radiation with much higher energies and can penetrate deeply into both the skin and underlying tissues, requiring dense materials such as lead or several centimeters of concrete to effectively shield against them.