What is radioactive carbon dating used for
As it's produced carbon-14 reacts with oxygen to form carbon dioxide and some of it is taken in by green plants and made into sugars along with the 'normal' carbon.
Carbon-14 is produced all the time but it also decays all the time back into nitrogen-14.
Carbon dating can be used to date things up to about 60 000 years old. Many people think that plants grow by taking food from the soil through their roots but this is not true. Animals eat plants (or other animals that eat plants) so animals are also mostly rearranged carbon dioxide.
All green plants make their own food in their leaves. A tiny fraction of carbon atoms are the radioactive isotope carbon-14.
Carbon-14 is produced in the upper atmosphere by cosmic rays.
It is a beta emitter with a half-life of about 5600 years.
We’re going to see what 'half-life' means and why radioactivity changes with time. It doesn’t depend on the size of the sample and it doesn’t change with time. So we imagine going in forward one half-life at a time from ZERO years: 10 years, 20 years, 30 years, etc.
We’ll also see how carbon dating can be used to date ancient remains. If we had a bigger sample of the same isotope then the count would be higher, say 200 becquerels. Then we halve the count for each half-life: 100 Bq after 10 years; 50 Bq after 20 years; 25 Bq after 30 years So we can see the radioactivity would be 25 becquerels afer 30 years.
For example, it might take 10 years for the count rate to drop from 80 Bq to 40 Bq; another 10 years to drop from 40 B to 20 Bq; another 10 years to drop from 20 Bq to 10 Bq and so on. The half-life of a particular isotope is always the same.
The unit of radioactivity is named after Henri Becquerel, who discovered it. A given isotope always takes the same amount of time for the count rate to decrease by a half.