By measuring the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of the artifact. To find it, type the N into your calculator and press the ln button) It is possible to show from this graph that the gradient is equal to -l called the decay constant.

As you can see from the graph, the steeper the gradient the more quickly the substance will decay and hence a shorter half-life.

It is possible to compare the activity of a living sample of material with an ancient specimen (of the same mass) and estimate the age.

For example if a specimen has half the activity of a living sample of equal mass it is around 5730 years old i.e. If the activity were quarter it would be 2 x 5730 = 11460 years old i.e.

To measure the amount of radiocarbon left in a artifact, scientists burn a small piece to convert it into carbon dioxide gas.

Radiation counters are used to detect the electrons given off by decaying Carbon-14 as it turns into nitrogen.

If the life of a radioactive substance is taken to mean the time that elapses before the activity drops to zero, then it is clear from the graph below that we would be waiting forever!

A much more useful quantity for dealing with the life of radioactive substances is the half-life.

However, at the moment of death, the amount of carbon-14 begins to decrease because it is unstable, while the amount of carbon-12 remains constant in the sample.

Half of the carbon-14 degrades every 5,730 years as indicated by its half-life.

The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant.

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