Question

The activity fo a radioactive sample decrases t `1//3` of the orginal acticity. `A_(0)` in a period of `9` year. After `9` year more, its activity will be:
A. `(A_(0))/(2)`
B. `(2A_(0))/(9)`
C. `(3A_(0))/(9)`
D. `(A_(0))/(9)`

Answer 1

Correct Answer - `(d)`
`t = (2.303)/(lambda) log ((r_(0))/(r))`
`9 = (2.303)/(lambda) log 3`
`:. lambda = 0.122`
Now `18 = (2.303)/(0.122) log ((r_(0))/(r_(2)))`
`:. (r_(2))/(r_(0)) = (1)/(9)`