Radioactive decay is exponential

The decay rate dN/dt is proportional to the number left.

Carbon-14 (¹⁴C) is produced in the atmosphere by cosmic ray bombardment of nitrogen nuclei. ¹⁴C residue can be used to date organic materials from buriel and other sites, if the ¹⁴C content of the atmosphere is known at the time of 'death' and no contamination is present.

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