The three types of nuclear emission — Identify

Identify alpha, beta and gamma emissions in terms of (a) their nature, (b) their relative ionising effects and (c) their relative penetrating abilities.

(a) Nature: an alpha particle is 2 protons and 2 neutrons bound together (a helium nucleus), charge +2; a beta particle is a fast-moving electron emitted from the nucleus, charge -1; gamma radiation is a high-frequency electromagnetic wave (photon), with no charge and no mass. (b) Ionising effect: alpha is the most strongly ionising, beta is less ionising than alpha, and gamma is the least ionising (alpha > beta > gamma). (c) Penetrating ability: alpha is the least penetrating, absorbed by a sheet of paper or a few cm of air; beta is more penetrating, absorbed by a few mm of aluminium; gamma is the most penetrating, only significantly reduced by many cm of lead or thick concrete (gamma > beta > alpha for penetration).