Particle radiation can be emitted from an unstable atomic nucleus (radioactive decay) in the form of a positively charged Alpha particle (α), a negatively charged Beta particle(β),a neutron, or Gamma rays (γ). Gamma rays are actually a form of electromagnetic radiation, but exhibit particle like properties due to their high energy.
Cosmic rays are subatomic particles falling naturally on the Earth. Most originate in the Sun and are part of the solar wind.
Radiation is often separated into two categories, ionizing and non-ionizing, to denote the energy and danger of the radiation. Ionization is the process of removing electrons from atoms, leaving two electrically charged particles (ions) behind. Some forms of radiation like visible light, microwaves, or radio waves do not have sufficient energy to remove electrons from atoms and hence, are called non-ionizing radiation. The negatively charged electrons and positively charged nuclei created by ionizing radiation may cause damage in living tissue. The term radioactivity generally refers to the release of ionizing radiation.
see radioactivity, radiation, physics, nuclear physics, nuclear engineering, radiation therapy
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