Half life dating rocks

Note the consequence of the law of large numbers: with more atoms, the overall decay is more regular and more predictable.A half-life usually describes the decay of discrete entities, such as radioactive atoms.U-235 decays to Pb-207 with a half-life of 704 million years.Due to its long half-life, U-235 is the best isotope for radioactive dating, particularly of older fossils and rocks. The half-life of C-14, however, is only 5,730 years.By comparing this ratio to the half-life logarithmic scale of the parent isotope, they are able to find the age of the rock or fossil in question.

For example, if there is just one radioactive atom, and its half-life is one second, there will not be "half of an atom" left after one second.For example, the image on the right is a simulation of many identical atoms undergoing radioactive decay.Note that after one half-life there are not exactly one-half of the atoms remaining, only approximately, because of the random variation in the process.For example, the medical sciences refer to the biological half-life of drugs and other chemicals in the human body. The original term, half-life period, dating to Ernest Rutherford's discovery of the principle in 1907, was shortened to half-life in the early 1950s.Rutherford applied the principle of a radioactive element's half-life to studies of age determination of rocks by measuring the decay period of radium to lead-206.

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