QUIZ 5 on RADIOACTIVITY - uses of radioisotope half-life data

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(a) During one half-life, of the radioactive atoms initially present in the sample and this fact can be used to materials.

(b) Certain isotopes, which have a half-life, decay via a series of relatively short-lived radioisotopes to produce stable isotopes of .

(c) The relative of uranium and lead isotopes in a sample of igneous rock can, therefore, be used to date the rock.

ns07.gifns06.gif(d) The proportions of the radioisotope potassium-, with protons and neutrons, and its stable decay product argon with protons and neutrons, can also be used by to date rocks from which the gaseous has been unable to escape.

(e) The same idea can be used by to date organic artifacts like wood and cloth from excavations using '' dating. The half-life of carbon-14 is 5700 years.

(f) If only 50% of the carbon-14 is left the object is years old. If only % of the carbon-14 is left, the artifact is 17100 years old.

(g) An organic object containing 25% of the original carbon-14 is years old. If only % of carbon-14 was left it would be 22800 years old!

(h) Half-life data is also important in choosing a radioactive isotope for a particular '' job.

(i) For example in medical examinations a radioisotope should have a half-life for reasons. However, in a smoke detector a half-life radioisotope is needed to avoid the alarm going off too soon as the signal changes too soon!