Carbon Dating

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Atomic and Nuclear Physics- Carbon dating

Carbon dating is a scientific technique in which scientists and archaeologists are able to estimate the age of materials such as wood through the decay of Carbon-14. This process can allow scientists to determine the age of such items up to about 58,000 and 62,000 years before the present time. Carbon dating was first discovered by Willard Libby in 1949 in which he was awarded a noble peace prize. Prior to this introduction, carbon dating has been used across the world to determine the age of old artefacts. Carbon dating in our atmosphere is produced by two sources. The first being the earth and the second being the cosmic rays that convert nitrogen into Carbon-14. Cosmic rays contain high levels of energy and can cause atoms in the upper atmosphere to split into pieces. Neutrons that are released as a result of this then crash into other molecules. When a single neutron collides with a nitrogen-14 atom present in the atmosphere it is converted into a carbon-14 atom.

Carbon-14 is an isotope of the element carbon. Its nucleus contains 6 protons and 8 neutrons. The radioactivity and stability of a nucleus is determined by the ration between neutrons and protons. Protons hold a positive charge whilst neutrons are neutrally charged. When the ratio between these sub atomic particles is too large or too small, the nucleus becomes unstable. The ratio between neutrons and protons in this isotope is too large, making the nucleus unstable and therefor radioactive. The ratio is too large due to their being 2 more neutrons to protons. This results in the isotope emitting a beta particle, causing Carbon-14 to be converted into nitrogen-14. On this earth, there are 3 naturally occurring isotopes of ...

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...d by a thin sheet of paper. Beta radiation on the other hand can penetrate air and paper but is stopped by a piece of aluminium. The most penetrating of the radioactive particles is gamma radiation. This form of radiation can pass through air, paper and aluminium and is only stopped by a thick piece of lead or a large amount of concrete.

Alpha particles can be stopped by a bit of air or a piece of paper. This is because as the particles travel through the air, they often collide with oxygen and nitrogen molecules. This collision results in the particles losing some of their energy whilst ionising the molecules present in the air. This process continues until all of the energy is lost and is absorbed. A sheet of paper on the other hand is a solid, thus the air molecules are much closer together resulting in the penetrability being much less in comparison to air.

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