They are of very high frequency radiation and are among the most dangerous for humans, as are all ionizing radiation. The danger derives from the fact that they are high-energy waves capable of irreparably damaging the molecules that make up the cells, which leads them to develop genetic mutations or even death.
On Earth we can observe natural sources of gamma rays both in the decay of radionuclides and in the interactions of cosmic rays with the atmosphere; more rarely the rays also produce this radiation.
Characteristics and Properties
Normally, the frequency of this radiation is greater than 10 20 Hz, so it has an energy greater than 100 keV and a wavelength less than 3x10 −13 m, much less than the diameter of an atom. Interactions involving gamma rays of energy from TeV to PeV have also been studied.
Gamma rays are more penetrating than radiation produced by other forms of radioactive decay, or alpha decay and beta decay, due to the lower tendency to interact with matter. Gamma radiation is made up of photons: this is a substantial difference from alpha radiation that is made up of helium nuclei and beta radiation that is made up of electrons; Photons, being not endowed with mass, are less ionizing. At these frequencies, the description of the phenomena of interactions between the electromagnetic field and matter cannot ignore quantum mechanics.
Gamma rays are distinguished from X-rays by their origin: gamma rays are produced by nuclear or subatomic transitions, in any case, while X-rays are produced by energy transitions due to electrons that enter external quantified energy levels in internal free energy levels more. As it is possible that some electronic transitions exceed the energies of some nuclear transitions, the frequency of more energetic X-rays may be greater than that of less energetic gamma rays. In fact, however, both are electromagnetic waves, as are radio waves and light.
Gamma Radiation Shield
The shielding of the γ rays requires much thicker materials than those necessary to protect the α and β particles that can be blocked with a simple sheet of paper (α) or a thin metal plate (β). Gamma rays are better absorbed by materials with a high atomic number and high density: in fact, if to reduce the intensity of a gamma ray by 50%, 1 cm of lead is required, the same effect is produced with 6 cm of cement 9 cm of pressed earth.
Protective materials are generally measured based on the thickness required to reduce the intensity of radiation by half. Obviously, the greater the energy of the photons., The greater the thickness of the shield required. Therefore, thick screens are needed for the protection of human beings, because gamma rays and x-rays produce effects such as burns, forms of cancer and genetic mutations. For example, in nuclear power plants to protect steel and cement are used in the particle containment vessel and water provides protection against radiation produced during storage of fuel rods or during transport of the reactor core nuclear.