19.6 Radioactive Tracers

19.6 Radioactive Tracers

A radioactive isotope behaves in just the same way as the normal isotope inside a living organism. But the location and concentration of a radioactive isotope can be determined easily by measuring the radiation it emits. Thus, a radioactive isotope acts as an indicator or tracer that makes it possible to follow the course of a chemical or biological process. The technique is to substitute radioactive atoms for stable atoms of the same kind in a substance and then to follow the 'tagged' atoms with the help of radiation detector in the process. For example, some chemicals such as hydrogen and sodium present in water and food are distributed uniformly throughout the human body. Certain other chemicals are selectively absorbed by certain organs. Radioisotopes of many elements can be made easily by bombardment with neutrons and other particles. As such isotopes have become available and are inexpensive, their use in medicine, agriculture, scientific research and industries has expanded tremendously. Radioisotopes are used to find out what happens in many complex chemical reactions and how they proceed. Similarly, in biology, they have helped in investigating into chemical reactions that take place in plants and animals. By mixing a small amount of radioactive isotope with fertilizer, we can easily measure how much fertilizer is taken up by a plant using radiation detector. From such measurements, farmers can know the proper amount of fertilizer to use. Through the use of radiation-induced mutations, improved varieties of certain crops such as rice, chickpea, wheat and cotton have been developed. They have improved plant structure. The plants have shown more resistance to diseases and pest, and give better yield and grain quality.

For your information

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Composition of Matter Molecule ($10^{-9}\,\mathrm{m}$) Atom ($10^{-10}\,\mathrm{m}$) Nucleus ($10^{-14} - 10^{-15}\,\mathrm{m}$) Neutron or Proton ($10^{-15}\,\mathrm{m}$) Quark (Less than $10^{-17}\,\mathrm{m}$)