Describe the different ways that radioactivity is used to measure the ages of different objects. Give...

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Physics

Describe the different ways that radioactivity is used tomeasure the ages of different objects. Give as much detail as youcan. Include such things as what is meant by the â€œageâ€ of anobject. Your write-up should be about 200-300 words for this partof the exercise.

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RADIOACTIVE DATINGRadioactive dating is a method of dating rocks and mineralsusing radioactive isotopes This method is useful for igneous andmetamorphic rocks which cannot be dated by the stratigraphiccorrelation method used for sedimentary rocksOver 300 naturallyoccurring isotopes are known Some do notchange with time and form stable isotopes ie those that formduring chemical reactions without breaking down The unstable ormore commonly known radioactive isotopes break down by radioactivedecay into other isotopesRadioactive decay is a natural process and comes from the atomicnucleus becoming unstable and releasing bits and pieces These arereleased as radioactive particles there are many types Thisdecay process leads to a more balanced nucleus and when the numberof protons and neutrons balance the atom becomes stableThis radioactivity can be used for dating since a radioactiveparent element decays into a stable daughter element at aconstant rate The rate of decay given the symbol is thefraction of the parent atoms that decay in unit time Forgeological purposes this is taken as one year Another way ofexpressing this is the halflife period given the symbol T Thehalflife is the time it takes for half of the parent atoms todecay The relationship between the two is T 0693 How is this radioactivity measuredMany different radioactive isotopes and techniques are used fordating All rely on the fact that certain elements particularlyuranium and potassium contain a number of different isotopes whosehalflife is exactly known and therefore the relativeconcentrations of these isotopes within a rock or mineral canmeasure the age For an element to be useful for geochronologymeasuring geological time the isotope must be reasonablyabundant and produce daughter isotopes at a good rateEither a whole rock or a single mineral grain can be dated Sometechniques place the sample in a nuclear reactor first to excitethe isotopes present then measure these isotopes using a massspectrometer such as in the argonargon scheme Others placemineral grains under a special microscope firing a laser beam atthe grains which ionises the mineral and releases the isotopes Theisotopes are then measured within the same machine by an attachedmass spectrometer an example of this is SIMS analysisWhat dating methods are thereRadiocarbon 14C datingThis is a common dating method mainly used by archaeologists asit can only date geologically recent organic materials usuallycharcoal but also bone and antlersAll living organisms take up carbon from their environmentincluding See Answer

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