Radiocarbon dating: The technique is used to find the age of historic and archaeological organic samples such as old wood samples and animal or human fossils.

Radioisotope used for carbon dating is ¹⁴C.

i. Radioactive¹⁴C is formed in the upper atmosphere by bombardment of neutrons from cosmic ray on ¹⁴N.

\(^{14}_7N\) + \(^{1}_0n\) \(\longrightarrow\) \(^{14}_6C\) + \(^{1}_1H\)

ii. ¹⁴C combines with atmospheric oxygen to form ¹⁴CO₂ which mixes with ordinary ¹²CO₂ . 

iii. This carbon dioxide is absorbed by plants during photosynthesis.

iv. Animals eat plants which have absorbed a carbon dioxide ( ¹⁴CO₂ + ¹²CO₂). Hence, ¹⁴C becomes a part of plant and animal bodies. v. As long as the plant is alive, the ratio ¹⁴C/ ¹²C remains constant

vi. When the plant dies, photosynthesis will not occur and the ratio ¹⁴C/ ¹²C decreases with the decay of radioactive ¹⁴C which has a halflife 5730 years.

vii. The decay process of ¹⁴C is given below: 

\(^{14}_6C\) \(\longrightarrow\) \(^{14}_7N\) + \(^0_{-1}e\)

viii. The activity (N) of given wood sample and that of fresh sample of live plant (N0) is measured, where, N0 denotes the activity of the given sample at the time of death. 

ix. The age of the given wood sample, can be determined by applying following Formulae:

t = \(\frac{2.303}{\lambda}\) log₁₀ \(\frac{N_0}N\)

Where \(\lambda\) = \(\frac{0.693}{5730\,y}\) = 1.21 x 10^-4 y^-1