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During nuclear explosion, one of the products is 90Sr with half-life of 28.1 years. If 1μg of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.

4.17   During nuclear explosion, one of the products is ^{90} Sr with half-life of 28.1 years. If 1 \mu g of ^{90}Sr  was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.

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M manish

Given,
half life = 21.8 years
\therefore\ k=0.693/t_{1/2}
           = 0.693/21.8
           

and, t = \frac{2.303}{k}\log\frac{[R]_{0}}{[R]}

by putting the value we get,

              10= \frac{2.303}{0.693/21.8}\log\frac{1}{[R]}
            \log[R] = -\frac{10\times 0.693}{2.303\times 21.8}
taking antilog on both sides,
[R] = antilog(-0.1071)
      = 0.781 \mu g

Thus 0.781 \mu g of {Sr}^{90} will remain after given 10 years of time.

Again, 


Thus 0.2278 \mu g of {Sr}^{90} will remain after 60 years.
              

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