Name a radioisotope that should be shielded by Plexiglass and not lead.

The correct answer is Phosphorous-32. This radioisotope emits beta particles, which can penetrate skin and cause damage. However, beta particles are effectively shielded by materials like Plexiglass, which can stop these particles from causing harm.

Using lead as a shield is typically reserved for gamma radiation or high-energy beta particles. While Phosphorous-32 can have more energetic emissions compared to some other isotopes, its beta radiation is adequately managed with a less dense material like Plexiglass. This makes it a suitable choice for shielding, as it is lighter and easier to handle than lead in terms of laboratory safety and operational efficiency.

The other isotopes mentioned, such as Carbon-14 and Tritium, either emit low-energy beta particles or are not considered high-risk in the same way, while Iodine-125 emits gamma radiation, which requires denser materials like lead for shielding effectively.