Which type of radiation is least penetrating?

Alpha radiation is classified as the least penetrating type of radiation among the options provided. This is primarily due to its composition and physical properties. Alpha particles consist of two protons and two neutrons, making them relatively large and heavy compared to other types of radiation like beta particles or gamma rays.

Because of their size, alpha particles have a very limited range in matter. They can be easily blocked by a sheet of paper or even the outer layer of human skin. This makes alpha radiation particularly safe in terms of external exposure, but it can be hazardous if alpha-emitting materials are ingested or inhaled, as they can cause significant damage to internal tissues at very close range.

In contrast, x-ray and gamma radiation are more penetrating. X-rays can pass through soft tissues but are stopped by denser materials, while gamma rays are highly penetrating and can traverse substantial thicknesses of material, including human tissue. Beta radiation, which consists of electrons, has moderate penetration abilities and can penetrate skin but is typically stopped by materials like plastic or glass.

Understanding the penetration abilities of different types of radiation is crucial for implementing effective safety measures in environments where radiation is present.