Which type of radiation poses the least risk to human health due to its low penetration ability?

Alpha particles are indeed the type of radiation that poses the least risk to human health due to their low penetration ability. These particles, consisting of two protons and two neutrons, carry a positive charge and are relatively heavy compared to other forms of radiation.

Their low penetration capability means that alpha particles can be stopped by a sheet of paper or the outer layer of human skin. As a result, they do not pose a significant hazard when outside the body. However, if alpha-emitting materials are ingested or inhaled, they can cause significant damage to internal tissues, but this situation is not typically encountered in everyday exposure scenarios.

This limited penetration capability is what ultimately makes alpha radiation less of a concern in terms of external exposure compared to other types of radiation, such as beta particles, gamma rays, and neutron radiation, all of which can penetrate deeper into biological tissues and thus have a higher potential for harmful effects.