Question

Explain the idea of carbon dating.

Answer 1

1. The interesting application of beta decay is radioactive dating or carbon dating. Using this technique, the age of an ancient object can be calculated. All living organisms absorb carbon dioxide (CO₂) from air to synthesize organic molecules. In this absorbed CO₂, the major part is \[\ce{^12_6C}\] and very small fraction (1.3 x 10^-12) is radioactive \[\ce{^14_6C}\] whose half-life is 5730 years.
   Carbon-14 in the atmosphere is always decaying but at the same time, cosmic rays from outer space are continuously bombarding the atoms in the atmosphere which produces \[\ce{^14_6C}\].
   So the continuous production and decay of \[\ce{^14_6C}\] in the atmosphere keep the ratio of \[\ce{^14_6C}\] to \[\ce{^12_6C}\] always constant.
2. Since our human body, tree or any living organism continuously absorb CO₂ from the atmosphere, the ratio of \[\ce{^14_6C}\] to \[\ce{^12_6C}\] in the living organism is also nearly constant. But when the organism dies, it stops absorbing C₂.
3. Since \[\ce{^14_6C}\] starts to decay, the ratio of \[\ce{^14_6C}\] to \[\ce{^12_6C}\] in a dead organism or specimen decreases over the years. Suppose the ratio of \[\ce{^14_6C}\] to \[\ce{^14_6C}\] in the ancient tree pieces excavated is known, then the age of the tree pieces can be calculated.