Changes must be reviewed before being displayed on this page. This article is about the term’s use in physics. However, a large fraction of such astronomical properties of alpha beta and gamma rays pdf rays are screened by Earth’s atmosphere and can only be detected by spacecraft.
However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. In astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, an energy far too large to result from radioactive decay. This historically allowed a clear distinction between X-rays and gamma rays. Today, the research literature often describes photons depending on their source. For example, one group of scientists might describe a 1 MeV photon as a gamma ray, while another group use the term X-ray. However, Villard did not consider naming them as a different fundamental type.
1903 named Villard’s rays “gamma rays” by analogy with the beta and alpha rays that Rutherford had differentiated in 1899. Gamma rays were first thought to be particles with mass, like alpha and beta rays. Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, proving that they were electromagnetic radiation.
A gamma decay was then understood to usually emit a single gamma photon. File:NASA’s Fermi Explores the Early Universe. Gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced. A large fraction of such astronomical gamma rays are screened by Earth’s atmosphere and must be detected by spacecraft.
A sample of gamma ray-emitting material that is used for irradiating or imaging is known as a gamma source. Gamma sources are usually sealed to prevent radioactive contamination, and transported in heavy shielding. It can then decay to a lower energy state by emitting a gamma ray photon, in a process called gamma decay. When high-energy gamma rays, electrons, or protons bombard materials, the excited atoms emit characteristic “secondary” gamma rays, which are products of the creation of excited nuclear states in the bombarded atoms. Formation of fluorescent gamma rays are a rapid subtype of radioactive gamma decay.