(sc) the emission of high-energy photons.
Gamma radiation is electromagnetic radiation of extremely short wavelength. Gamma radiation ranges in energy from about 10-15 to 10-10 J (10 keV to 10 MeV) (wavelength less than about 1 pm). Gamma rays are emitted by excited atomic nuclei during the process of passing to a lower excitation state. Gamma rays are extremely penetrating and are absorbed by dense materials like lead and uranium. Exposure to gamma radiation may be lethal.
A high-energy electromagnetic, ionizing radiation that comes from the nucleus of an atom undergoing radioactive decay. Gamma rays are similar to medical X-rays but are emitted at very specific energies characteristic of their decaying atoms. Gamma rays penetrate body tissues and may damage cells. People exposed to the atomic bombings of Hiroshima and Nagasaki were exposed to gamma radiation. Cesium-137 is a source of gamma radiation.