Final answer:
A barrier is designed to protect against direct radiation including unscattered radiation such as alpha and beta particles, and high-penetration radiation like gamma rays and X-rays, by using materials like paper, metal, lead, or concrete for shielding.
Step-by-step explanation:
The barrier mentioned in the question is designed to prevent various types of radiation from reaching personnel or members of the general public. Among the types of radiation, it would prevent direct radiation, which includes unscattered radiation like alpha and beta particles, and high-penetration forms such as gamma rays and X-rays. In summary:
- Alpha particles, being the least penetrating, can usually be stopped by a thin barrier such as paper or skin cells.
- Beta particles can pass through thin materials but are stopped by a layer of metal.
- Gamma rays and X-rays are highly penetrating and require thick or dense barriers like lead or concrete for effective attenuation.
Shields are essential for radiation protection and are used to reduce exposure by blocking or attenuating direct, scattered, and high-energy indirect radiation.