alpha particle A nuclear particle identical to a helium nucleus with symbol α or 4/2He
becquerel (Bq) A unit of activity of a radioactive sample equal to one disintegration per second.
beta particle A particle identical to an electron with symbol β or 0/-1 e that forms in the nucleus when a neutron changes to a proton and an electron.
carbon dating A technique used to date ancient specimens that contain carbon. The age is determined by the amount of active carbon-14 that remains in the samples.
chain reaction A fission reaction that will continue once it has been initiated by a high-energy neutron bombarding a heavy nucleus such as uranium-235.
curie (Ci) A unit of radiation equal to 3.7 x 1010 disintegrations/s.
decay curve A diagram of the decay of a radioactive element.
equivalent dose The measure of biological damage from an absorbed dose that has been adjusted for the type of radiation.
fission A process in which large nuclei are split into smaller pieces, releasing large amounts of energy.
fusion A reaction in which large amounts of energy are released when small nuclei combine to form larger nuclei.
gamma ray High-energy radiation (with symbol $7) that is emitted by an unstable nucleus.
gray (Gy) A unit of absorbed dose equal to 100 rads.
Half-life The length of time it takes for one-half of a radioactive sample to decay.
positron A particle with no mass and a positive charge produced when a proton is transformed into a neutron and a positron.
rad (radiation absorbed dose)
rad (radiation absorbed dose) A measure of an amount of radiation absorbed by the body.
radiation Energy or particles released by radioactive atoms.
radioactive decay The process by which an unstable nucleus breaks down and releases high-energy radiation.
rem (radiation equivalent in humans)
rem (radiation equivalent in humans) A measure of the biological damage caused by the various kinds of radiation (rad X radiation biological factor).
scan The image of a site in the body created by the detection of radiation from radioactive isotopes that have accumulated in that site.
shielding Materials used to provide protection from radioactive sources.
sievert (Sv) A unit of biological damage (equivalent dose) equal to 100 rems.