Carbon`-14` used to determine the age of organic material. The procedure is absed on the formation of `C^(14)` by neutron capture iin the upper atmosphere.
`._(7)N^(14)+._(0)n^(1) rarr ._(6)C^(14)+._(1)H^(1)`
`C^(14)` is absorbed by living organisms during photosynthesis. The `C^(14)` content is constant in living organism. Once the plant or animal dies, the uptake of carbon dioxide by it ceases and the level of `C^(14)` in the dead being falls due to the decay, which `C^(14)` undergoes.
`._(6)C^(14)rarr ._(7)N^(14)+beta^(c-)`
The half`-` life period of `C^(14)` is 5770 year. The decay constant `(lambda)` can be calculated by using the following formuls `:`
`lambda=(0.693)/(t_(1//2))`
The comparison of the `beta^(c-)` activity of the dead matter with that of the carbon still in circulation enables measurement of the period of the isolation of the material from the living cycle. The method, however, ceases to be accurate over periods longer than 30000 years. The proportion of `C^(14)` to `C^(12)` in living matter is `1:10^(12)`.
What should be the age of fossil for meaningful determination of its age ?

Options

A. In living organisms, circulation of `.^(14)C` from the atmosphere is high, so the carbon content is constant in organism.
B. Carbond dating can be used to find out the age of earth crust and rocks.
C. Radioactive absorption due to cosmic radiation is equal to the rate of radioactive decay. Hence, the carbon content remains constant in living organisms.
D. Carbon dating cannot be used to determine concentration of `C^(14)` in dead beings.

Answer

C

Explanation

Radioactive absorption due to cosmic radiation is equal to the rate of radiactive decay, hence the carbon content as the ratio of `C^(14)` remains constant in living organism.