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18 July, 07:28

Dinosaur fossils are often dated by using an element other than carbon, like potassium-40, that has a longer half life (in this case, approximately 1.25 billion years). suppose the minimum detectable amount is 0.1% and a dinosaur is dated with 40k to be 67 million years old. is this possible?

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  1. 18 July, 07:56
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    The equation relating radioactive decay is:

    N (i) = N (o) * exp (-0.693*t / t (half))

    The fraction:

    N (i) / N (o) represents the fraction of original substance present after t years and a half-life of t (half). Substituting the values,

    N (i) / N (o) = exp ((-0.693 * 67) / (1,250))

    N (i) / N (o) = 0.964 or 96.4%

    This means that the amount is far above the minimum detectable amount, so this method is feasible.
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