One of the hazards of explosion is the generation of `Sr""^(90)` and its subsequent incoperation in bones. This nuclide has a half life of 2.81 years. Suppose one microgram was absorbed by a new born chiled,how much `Sr""^(90)` will remain in his bone after 20 years?

Explanation

`t""_(1//2)" of "Sr""^(90)=28.1yr=(0.693)/(t""_(1//2))=(0693)/(28.1)yr""^(-1)`
`"Initial conc. of " Sr""^(90)=10""^(-6)g=1mug`
`" Let N be the conc. of "Sr""^(90)" left after 20 years = N"`
`"t = 20 years"`
`lamda=(2.303)/(t)log.(N""_(0))/(N)," "(0.693)/(28.1)=(2.303)/(20)log.(N""_(0))/(N)`
`log.(N""_(0))/(N)=(20xx0.693)/(28.1xx2.303)=0.2141`
`"Taking anti logarithm"`
`(N""_(0))/(N)=1.6375" "," "N=(1)/(1.6375)mug=0.6107mug`