Step by step process of carbon dating
This technique works well for materials up to around 50,000 years old.
Each radioactive isotope decays by a fixed amount, and this amount is called the half-life.
Radioactive carbon-14 is continually formed in the atmosphere by the bombardment of cosmic ray neutrons on nitrogen-14 atoms.
After it forms, carbon-14 naturally decomposes, with a half-life of 5,730 years, through beta-particle decay.
By measuring the amount of carbon-14 left in the organism, it's possible to work out how old it is.
For the record, a beta-particle is a specific type of nuclear decay. Image 1 shows carbon-14 production by high energy neutrons hitting nitrogen-14 atoms, while in Image 2, carbon-14 naturally decomposes through beta-particle production.
Notice that the nitrogen-14 atom is recreated and goes back into the cycle.
Scientists often use the value of 10 half-lives to indicate when a radioactive isotope will be gone, or rather, when a very negligible amount is still left.
This is why radiocarbon dating is only useful for dating objects up to around 50,000 years old (about 10 half-lives).