# Half life radiometric dating element

Correction tables are used to correct 'raw' radiocarbon dates (quoted as years ad or ).The method yields reliable dates back to about 50,000 bp and under some conditions to about 75,000 bp.This is now a common method for estimating the age of a carbonaceous archaeological artifacts.The radioactivity of an artifact's content determines how long ago the specimen was separated from equilibrium with the atmosphere-plant-animal cycle.Determination of the radioactivity of carbon from a sample will reveal the proportion of C14 to C12, and this will in turn, through the known rate of decay of C14, give the age of, or more accurately the time elapsed since the death of, the sample.Two things in the method have to be allowed for: first, the 'date' given is never exact.

Constituent elements and concentrations are identified by the characteristic energy spectrum of emitted rays and their intensity.

The /- figure, which should always be quoted, is a statistical one, meaning that there is a 2 to 1 chance that the correct date lies within that bracket.

Secondly, the rate of decay of C14 is based in all published examples on a of 5730 /- 40 years (after 5730 years, one half of the C14 will have disintegrated, after another 5730 years one half of the remainder, and so on).

One of the basic assumptions of the technique is that the amount of radiocarbon in the atmosphere has remained constant through time.

It has now been established, with the dendrochronological sequence for the , that the C14 concentration has fluctuated.