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  1. The technique used to determine the age of a fossil is Carbon dating from the activity of C14 isotope present in it.
  2. High energy cosmic rays bombard the upper atmosphere producing large number of neutrons.
  3. These neutrons collide with nitrogen in the air changing some of it into Carbon-14.
    7N14 + 0n1 ―――――→ 6C14 + 1H1
  4. The radioactive carbon combines with oxygen in the upper atmosphere and forms CO2 which diffuses down to earth and is absorbed by plants and animals.
  5. Carbon from plants or living organisms radiates β-particles and a definite proportion of C14 isotope to C12 isotope is maintained in all plants and living organisms.
    6C14 ―――――→ 7N14 + -1e0
  6. When the plant or animal dies, the intake of carbon-14 stops and the C14 activity decreases. By comparing the radioactivity from present day plant or animals (N0) with that of the given fossil (N), the age of the fossil can be accurately calculated by using the formula given below: