Unit #2 Glossary of Terms

ALARA:  “As Low As Reasonably Achievable”   Personnel working in the field are required to keep their radiation exposures ALARA.

Atom: The fundamental basic building block of matter made up of three subatomic particles called protons, neutrons, and electrons.  The basic unit of a chemical element of the periodic chart.

Curie:  (Ci) is the unit of measurement of the amount of radioactivity of a substance, named after Marie and Pierre Curie.    1 Ci = 3.7×1010 disintegrations per second (rate of decay)

Becquerel (Bq) – Si unit for measuring radioactivity.

Electromagnetic spectrum: A continuum of electric and magnetic radiation encompassing all wavelengths.

Electron: a stable subatomic particle with a charge of negative electricity, found in all atoms.

Ion: an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.  A positively or negatively charged atom or molecule.

Ionization:  The removal of electrons from an atom.  The essential characteristic of high-energy radiations when interacting with matter.

Ionizing Radiation:  a type of radiation that is able to disrupt atoms and molecules on which they pass through, giving rise to ions and free radicals.

Isotopes: atoms with same atomic number and chemical properties as element atoms; the nucleus has same number of protons but a different number of neutrons and thus, a different atomic mass.

Neutron:  a subatomic particle with about the same mass as a proton but without an electric charge.  Neutrons are present in all atoms except the Hydrogen atom.

Particulate (or particle) Radiation:  is the radiation of energy by means of fast-moving subatomic particles.  Alpha particles, Beta particles, neutrons, and positrons are examples of particulate radiation.

Photons: Discrete particles of light or electromagnetic radiation hypothesized to explain the corpuscular theory of radiant energy.

Proton:  a subatomic particle present in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron, but of opposite sign.

Radiant energy (Qe): Energy transmitted through a medium by electromagnetic waves. Also known as radiation.

Radiation: Energy in transit. Either as particles or electromagnetic waves.

Radioactivity:  The characteristic of various materials to emit ionizing radiation.

Roentgen (R) – is a unit of measurement to the exposure of ionizing radiation, specifically Gamma radiation and X-rays, named after the German physicist.

SI: The International System of units of measurement. Includes most of the base units formerly called metric.

X-ray – a type of ionizing radiation formed in a Cathode Ray Tube (CRT) when high velocity electrons flow from the cathode to the anode.

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Radiation Safety by J. S. Ballard is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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