To protect against alpha radiation, which barrier provides minimum protection?

• A. Glass Window
• B. Sheet of Paper
• C. Plastic Wrap
• D. Lead Shield

Answer: (B)

Alpha radiation has very low penetrating power; it can be stopped by a thin barrier like paper or even a layer of skin. Because the goal is to block these particles with the smallest practical barrier, a sheet of paper is the minimal protective material that reliably stops alpha radiation. A thinner or similarly thin barrier could also stop alpha, but paper is the classic example of the least necessary shield that provides protection. Lead, glass, or other thicker barriers are unnecessary for alpha and would be more than what’s needed in typical shielding, whereas paper is just enough.