Uses of Radioisotopes

Tracer Applications

         

 A radioisotope used to follow the path of chemical process is called a tracer. The fact that it can be detected or “traced” as it decays make it possible to determine its location at all times. Carbon-14 is the most useful tracer isotope, and has been used to study photosynthesis and the pathway followed by carbon in many organic processes.

Radiation Applications

      

Some radioisotopes are used in the treatment of cancer because they have the ability to kill living tissues. Radium and cobalt release intense radiation which is used to destroy tumor cells.

Radiation can also be used to treat foods and grains. Molds, bacteria, yeasts and insect eggs in food samples can be destroyed by irradiation to prolong their shelf-life

Industrial applications of radiation are now widely used like the tracking of the uniformity of plastic films and paper stock.

Dating application

Since half-life of a radioisotope is not affected of pressure and temperature, it is assumed that it decays at a constant rate. For example, C-14 decays by beta decay.

¹⁴₆C → ¹⁴₇N + ⁰_-1e

The ratio of C-14 to C-12 in the atmosphere has remained constant for thousands of years. Plant use C0₂ during photosynthesis. Animals which eat the plant will have C-12and C-14 in their tissues. When the plant or animal dies, the amount of C-14 become less and less as it decays. By comparing the amount of C-14 that remains to the amount of C-12 that is present, the amount of C-14 that has decayed can be measured.

The half-life of C-14 is 5,700 years. If a sample of wood show that the ratio of C-14 to C-12 is only one-half of the ratio, it can be deduced that the wood is 5,700 years old.

In dating minerals, the U-238 à Pb-206 present represents the amount of U-238 that decayed. Calculation based on this method indicate that the earth is about 4.5 billions years old.

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