Which type of radiation has the greatest penetration power?

• A. Alpha radiation
• B. Gamma radiation
• C. Beta radiation
• D. X-ray radiation

Answer: (B)

The main idea here is how deeply different types of radiation can pass through matter. Penetration power depends on being able to pass through materials without being absorbed or scattered a lot. Alpha particles are heavy and carry a charge, so they interact strongly with matter and are stopped very easily—by a sheet of paper or a few centimeters of air. Beta particles are lighter and carry a charge, so they penetrate more than alpha but can be stopped by a thin sheet of metal. Gamma rays are high-energy photons with no mass and no charge, so they interact much less with matter and can pass through thicker materials. X-rays are also electromagnetic waves and can penetrate, but gamma rays—originating from nuclear transitions—generally have higher energy and therefore greater penetration. So, gamma radiation has the greatest penetration power among these.