Holt McDougal Physics:
Use of Carbon Dating Radioactive carbon is continually formed in the atmosphere by the bombardment of cosmic ray neutrons on nitrogen atoms.
This CO 2 is used in photosynthesis by plants, and from here is passed through the food chain see figure 1, below.
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Description: There are also trace amounts of the unstable radioisotope carbon 14 C on Earth. Carbon is a radioactive isotope of carbon.