Rubidium-strontium dating. The rubidium isotope 8737Rb, a β emitter with a half-life of 4.75×1010yr, is used...

Rubidium-strontium dating. The rubidium isotope 8737Rb, a β emitter with a half-life of 4.75×1010yr, is used to determine the age of rocks and fossils. Rocks containing fossils of ancient animals contain a ratio of 8738Sr to 8737Rb of 0.0310.

Assuming that there was no 8738Sr3887Sr present when the rocks were formed, estimate the age of these fossils.

Solutions

Expert Solution

Radioactive decay of into is given below

Half life is 4.75 1010 years

Ratio of to found in the fossils of ancient animal = 0.031

Hence fraction of undecayed atoms = 0.969

Hence from radioactive decay equation, we get

where T is half-life period of

ln(0.969) = [ -ln2 t ] / ( 4.75 1010 )

Hence age of rocks and fossil, t = - [ ln(0.969) / ln(2) ] ( 4.75 1010 ) year

t = 2.158 1010 year

genius_generous answered 1 year ago

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