The three types of nuclear emission — Explain

Explain why alpha, beta and gamma radiations have different relative ionising effects, with reference to kinetic energy and electric charge.

(a) Kinetic energy: alpha particles are relatively heavy and move comparatively slowly for a given energy, so they spend more time close to each atom they pass, transferring energy and removing electrons frequently over a short distance - causing intense, localised ionisation. Beta particles are much lighter and move faster, so they spend less time near each atom and ionise less frequently per unit distance travelled. (b) Electric charge: alpha particles carry a large charge (+2), so they exert a strong electric force on the electrons of atoms they pass, easily removing electrons and causing strong ionisation. Beta particles carry a smaller charge (-1), so exert a weaker force and cause less ionisation. Gamma radiation is uncharged, so it interacts only weakly with atoms and produces the least ionisation of the three.