In paper mills, the thickness of the paper can be controlled by measuring how much beta radiation passes through the paper to a Geiger counter. The counter controls the pressure of the rollers to give the correct thickness. With paper, or plastic, or aluminium foil, b rays are used, because a will not go through the paper.

What is Carbon Dating? The age of archaeological specimens can be calculated by looking at the amount of carbon - 14 in a sample. The method is a form of radio dating called carbon dating.

How long does material remain radioactive? Practice revision questions on half-life calculations and radioactive decay. Problem solving using the half-life of a radioisotope or radioactive emission data to work out the half-life of a radioactive isotope.

Firstly radioactive decay is completely random, that means you cannot predict which nucleus will decay or when it will decay. There is however a set probability of radioactive decaying during any given second, when you get down to it Nuclear Physics does come down to probabilities, that's Heisenburg's uncertainty principle and Schrodinger's Cat analogy is all about. But I digress. You have to remember that we are dealing with huge numbers of radioactive nuclei, for example in a 1kg sample of Uranium there are 2.

Radiocarbon or Carbon dating is a technique used by scientist to date bones, wood, paper and cloth. Carbon is a radioisotope of Carbon. The unstable Carbon is transported down to the lower atmosphere by atmospheric activity such as storms.

Carbon has a large number of stable isotopes. All carbon atoms contain six protons and six electrons, but the different isotopes have different numbers of neutrons. The amount of carbon in the atmosphere has not changed in thousands of years.

The carbon content of living trees includes a small proportion of carbon, which is a radioactive isotope. After a tree dies, the proportion of carbon in it decreases due to radioactive decay. The age of an ancient boat may be determined by comparing the radioactive decay of from living wood with that of wood taken from the ancient boat.

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Some rock types such as granite contain traces of uranium. All uranium isotopes are radioactive. These uranium isotopes go through a series of decays, eventually forming a stable isotope of lead. By comparing the amounts of uranium and lead present in a rock sample, its approximate age can be found.