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A gamma ray, also known as gamma radiation (symbol γ), is a penetrating form of electromagnetic radiation typically arising from the radioactive decay of atomic nuclei.It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays.
The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and ...
Gamma-ray astronomy is a subfield of astronomy where scientists observe and study celestial objects and phenomena in outer space which emit cosmic electromagnetic radiation in the form of gamma rays, [nb 1] i.e. photons with the highest energies (above 100 keV) at the very shortest wavelengths. Radiation below 100 keV is classified as X-rays ...
Ionizing radiation has many industrial, military, and medical uses. Its usefulness must be balanced with its hazards, a compromise that has shifted over time. For example, at one time, assistants in shoe shops in the US used X-rays to check a child's shoe size, but this practice was halted when the risks of ionizing radiation were better ...
The region at which radiation is considered "ionizing" is not well defined, since different molecules and atoms ionize at different energies. The usual definitions have suggested that radiation with particle or photon energies less than 10 electronvolts (eV) be considered non-ionizing. Another suggested threshold is 33 electronvolts, which is ...
The radiation emitted covers the entire electromagnetic spectrum and the intensity of the radiation (power/unit-area) at a given frequency is described by Planck's law of radiation. For a given temperature of a black-body there is a particular frequency at which the radiation emitted is at its maximum intensity.
In interplanetary space, however, it is believed that thin aluminium shielding would give a net increase in radiation exposure; thicker shielding would be needed to block the secondary radiation. [35] [36] Studies of space radiation shielding should include tissue- or water-equivalent shielding along with the shielding material under study.
According to Kirchhoff's law of thermal radiation, this entails that, for every frequency ν, at thermodynamic equilibrium at temperature T, one has α ν,B (T) = ε ν,B (T) = 1, so that the thermal radiation from a black body is always equal to the full amount specified by Planck's law. No physical body can emit thermal radiation that exceeds ...