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 `16.1`counts 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

Options

A. artifical transmutation
B. cosmic neutron bombardment of nitrogen
C. it being a part of radioactive series happening naturally
D. `.^(12)C` when gets bombarded with neutrons, transmutes to `.^(14)C` in environment

Answer

B