Which radiation is known to have significant penetrating power and is more hazardous externally?

Neutrons are known for their significant penetrating power due to their lack of an electric charge, which allows them to travel through matter more easily than charged particles like alpha or beta particles. Unlike alpha particles, which can be stopped by a sheet of paper, and beta particles, which can be reduced by plastic or aluminum, neutrons can penetrate deeper into materials, including biological tissue. This makes them more hazardous when there is external exposure, as they can pass through the body and interact with internal organs.

Additionally, neutrons can induce secondary radiation when they interact with other materials, further increasing the potential for biological damage. Therefore, in the context of external exposure risks, neutrons pose a significant hazard due to their penetrating capabilities and the subsequent effects they can have within the body.

In contrast, beta particles and alpha particles, while also harmful, do not equal the penetrating power of neutrons and are less concerning for external exposure. X-rays are also penetrating but usually not as highly regarded for external hazards in comparison to neutrons when considering direct interactions and potential for biological effects.