Causes of Radiation
When a proton or neutron shifts between cells within the nucleus, it releases gamma radiation. Atoms release particle radiation during radioactive decay; most emit gamma radiation as well, as their protons and neutrons shift between shells. During nuclear reactions, radiation is emitted as protons, neutrons, and electrons shift between shells; for example, in nuclear fission, when a nucleus splits into two, particles move to the shells of the new nuclei.
Electromagnetic radiation is released when an electrically charged particle changes direction, or speed, or both. A particle that enters an electric or magnetic field, for example, slows down and shifts direction and, therefore, emits radiation. Whenever electrons lose speed suddenly, such as when in an x-ray machine they collide with metal atoms, x-rays form. X-rays form when electrons pass a large nucleus as well. The nucleus, which has a positive charge, draws electrons, which have a negative charge. As the electrons change direction, they produce x-rays called bremsstrahlung, a German word that means braking radiation.
Depending on the energy electrons have, they may be found at varying distances from the nucleus, in regions called electron shells. Electrons with little energy are found in inner shells, and those with high energy are found in outer shells. In the nucleus, protons and neutrons are arranged in layers, called nuclear shells according to their energy levels. All the particles in a shellprotons, neutrons, and electronshave almost identical quantities of energy.
Electrons seek the state of lowest energy. When an electron shifts from an outer shell to one closer to the nucleus, the electron discharges energy in the form of a photon, which moves away from the atom. The difference in energy of the original shell of the electron and its new shell is the photons energy. If the difference is small the atom will emit visible light, infrared radiation, or both. If the difference is large, the atom will emit x-rays.