Practice question

Penetration ability inversely correlates with ionization density and mass. Alpha particles are massive helium nuclei with two positive charges interacting heavily, stopped by paper or few centimeters of air. Beta electrons are smaller, more penetrating to millimeters of aluminum. Gamma rays and X-rays are massless photons with no charge, interacting only occasionally, traversing centimeters of lead and entire human body. This high mass and charge explains why alpha radiation delivers intense damage over short range but cannot penetrate skin, defining its lowest penetrating power.