Biologically useful technetium nuclei (with atomic weight 99) have a half life of 6 hrs. A solution containing `10^(-12)` g of this is injected into the bladder of a patient. Find its activity in the beginning and after one hour.

Explanation

Here, T=6 hrs.
Number of of technetium atoms in `10^(-12)g` in the
beginning
`N_0=("Avogadro's number")/("atomic weight")xx10^(-12)`
`=(6.023xx10^(23)xx10^(-12))/99=6.08xx10^9`
Activity in the beginning,
`A_0=lambdaN_0=0.693/TN_0`
`A_0=0.693/6xx6.08xx10^9=7.02xx10^8h^-1`
After 1 hr. number of tech. atoms left
`N=N_0e^(-lambda t)=6.08xx10^9e^(-0.693/6xx1)`
`=5.423xx10^9`
`:.` Activity after 1 hour
`R=lambdaN=0.693/6xx5.423xx10^9`
`=6.264xx10^8h^-1`.