Radioactive dating uses the ratios of isotopes and their specific decay products to determine the ages of rocks, fossils, and other substances. ScienceFusion Matter and Energy: Examples of questions on this material that could be asked on an exam Which isotopic systems are most useful for radiometric dating and what are the limitations of each?
Plotting an isochron is used to solve the age equation graphically and calculate the age of the sample and the original composition. Anything which changes the relative amounts of the two isotopes original and daughter must be noted, and avoided if possible. Each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life or, in other words, the time required for a quantity to fall to half of its starting value. Stimulating these mineral grains using either light optically stimulated luminescence or infrared stimulated luminescence dating or heat thermoluminescence dating causes a luminescence signal to be emitted as the stored unstable electron energy is released, the intensity of which varies depending on the amount of radiation absorbed during burial and specific properties of the mineral. In many cases, the daughter nuclide itself is radioactive, resulting in a decay chain , eventually ending with the formation of a stable nonradioactive daughter nuclide; each step in such a chain is characterized by a distinct half-life. Uranium is not the only isotope that can be used to date rocks; we do see additional methods of radiometric dating based on the decay of different isotopes. Thus, as an event marker of s water in soil and ground water, 36 Cl is also useful for dating waters less than 50 years before the present.