Gamma Radiation

Gamma radiation ( γ ) is a form of high energy electromagnetic radiation and is another form of ionizing radiation. Gamma emission occurs primarily after the emission of a decay particle (such as an alpha or beta particle). After a particle is ejected from a nucleus the system may have some slight excess of energy or exist in a metastable state. This slight excess of energy is released as gamma rays.

Gamma radiation, discovered by P. Villard, is unlike alpha and beta radiation (recall that an alpha particle has the mass of a helium nucleus and beta particles have the mass of electrons). Gamma radiation has no mass, no electrical charge, and is highly energetic.

Since gamma rays have no mass, they are the most penetrating form of radiation and the most destructive to biological systems. A gamma ray can pass entirely through the human body and not be stopped. It would take 10 cm of lead to stop gamma rays. Gamma emission is a significant health risk. Gamma rays are best stopped by lead, iron, or concrete.