Which material acts as an effective shield for alpha radiation?

Alpha radiation consists of positively charged particles (helium nuclei) that are relatively large and heavy compared to other forms of radiation such as beta and gamma radiation. Due to their size and charge, alpha particles have low penetration ability. They can be effectively stopped by very thin materials.

Both cardboard and plastic are effective in shielding against alpha radiation. In fact, even a sheet of paper or the outer layer of human skin can block alpha particles. This makes materials like cardboard and plastic suitable for use in specific contexts where alpha radiation is a concern.

The option indicating "All of the above" captures the fact that both cardboard and plastic can provide sufficient shielding from alpha radiation, making it the correct answer. Additionally, while lead is often used as a shield against gamma radiation and is very effective for that purpose due to its high density and atomic number, it is not the primary material used for shielding against alpha radiation. The key to understanding this question lies in recognizing the effectiveness of lightweight and less dense materials against alpha particles.