Radioactive dating of organic materials

The trees are themselves dated by the carbon-14 method using dead parts in the bark.A comparison between the carbon date and that due the tree rings is shown in the diagram.When smoke gets into the detector the alpha particles cannot get through to the sensor and the alarm goes off.Bacteria in food can be killed if exposed to gamma radiation.Therefore A = A If a little radioactive material is put into a moving liquid the path of this liquid can be tracked.Used in testing blood flow, tracking underground streams and following the movement of silt in rivers A beta source is put on one side of a sheet of material and a Geiger counter on the other.A form of radiometric dating used to determine the age of organic remains in ancient objects, such as archaeological specimens, on the basis of the half-life of carbon-14 and a comparison between the ratio of carbon-12 to carbon-14 in a sample of the remains to the known ratio in living organisms. A technique for measuring the age of organic remains based on the rate of decay of carbon 14.The carbon 14 present in an organism at the time of its death decays at a steady rate, and so the age of the remains can be calculated from the amount of carbon 14 that is left. The cells of all living things contain carbon atoms that they take in from their environment.

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A similar sample of fresh bone gives a count rate of 19 counts per minute. The activity A of a sample is proportional to the number of radioactive atoms within it.

As soon as the animal dies the intake of radioactive carbon-14 stops and the proportion in the body starts to decrease.

Therefore if the proportion of carbon 14 to carbon 12 is known at the start, the age of the specimen can be found once the amount of carbon 14 remaining in it has been measured.

Carbon 14 is continually being created in the Earth's atmosphere by the interaction of nitrogen and gamma rays from outer space.

Since atmospheric carbon 14 arises at about the same rate that the atom decays, the Earth's levels of carbon 14 have remained constant.

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