1.

The quantity of .^(14)C as well as that of .^(14)CO_(2) present in the atmosphere remains constant. The concentration of .^(14)C in all living organisms remains almost constant during their life time. After their death, .^(14)C is not taken up by them but the content of .^(14)C assimilated begins to decay by emitting beta- particles, with half-life period of 5568 years. The decay rate at the time of death of plant is 16.1counts per minute per gram of carbon. Hence, by measuring the decay rate of the dead matter, the age of matter can be calculated , e.g. if decay rate of sample of wood is found to be N distengrations per minute per gram of carbon after t years, then N=N_(0)e^(-lambda t) where lambda= disntegration constant and N_(0)= number of disntegrations per minute per gram when the plant had just died. .^(14)C is present in environmental because of

Answer»

artifical transmutation
cosmic neutron bombardment of nitrogen
it being a part of radioactive SERIES happening naturally
`.^(12)C` when GETS bombarded with neutrons, TRANSMUTES to `.^(14)C` in environment

Answer :B


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