# Carbon Dating

**Carbon dating**

W.F. Libby (1950)has shown that by measuring the radioactivity of it is possible to calculate the date at which a plant was cut or an animal died. The principle of this technique is that is produced in the upper atmosphere as:

There is one atom of for every carbon atom in the of the atmosphere and in all living animals and plants. This ratio always remains constant in nature. when the animal or plant dies starts disintegration as:

Thus by measuring the radioactivity of the substance under consideration and knowing the of the is is possible to calculate when the sample was removed from the carbon cycle.

Rock dating: use to find age of earth crust, rocks etc. it is based on the fact that U-238 decays to give Pb-206. [ of years]

**Formulae**

Mass Defect = Expected mass – Actual mass

Binding energy,

**Example 1**: A piece of charcoal from the ruins of a settlement in japan was found to have a ratio that was 0.617 times that found in living organisms. How old is this piece of charcoal? The half-life period of is 5770 years.

Solution:

From eq.3,

From eq.2,

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