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Q.
The half-life of radium is $1600\, yr$. What fraction of sample of radium will be disintegrated after $6400\, yr$?
Delhi UMET/DPMTDelhi UMET/DPMT 2002
Solution:
As radioactive decay is first-order kinetic half-life given is 1600 years in 6400 no. of half-life is
$
n =\frac{6400}{1600}=4
$
fraction of element remains after $n$ half life is given $b y=\frac{1}{2^{n}}$ Hence fraction of radium remains after 4 half life $=\frac{1}{2^{4}}=\frac{1}{16}$.