Which of the following can stop a beta particle?

• A. Wood
• B. Lead
• C. Concrete
• D. Water

Answer: (A)

Beta particles are fast electrons with limited penetrating power. They lose energy mainly by ionizing atoms in the material they pass through, so a barrier that isn’t too dense and has a modest thickness can stop them effectively. Wood fits this role well because it’s a low-density, low–atomic-number material, so a reasonable thickness can absorb most beta particles without producing significant secondary radiation. Lead, while capable of stopping betas, is high in density and can generate bremsstrahlung X-rays when beta particles interact with it, which may require additional shielding. Concrete and water would also stop betas but typically need thicker barriers to achieve the same stopping effect as a thinner wood shield. So, wood is the most practical barrier among the options for stopping a beta particle.