If one starts with one curie of radioactive substance `(T_(1//2) = 12 hrs)` the activity left after a period of `1` week will be about

Options

A. 1 curie
B. 120 micro curie
C. 60 micro curie
D. 8 mili curie

Answer

C

Explanation

( c) `1 "week" ~~ 7 "days" = 7 xx 24 hrs ~~ 14` half lives
Number of atoms left `(N_0)/((2)^14)` Activity `= N lambda`
`:.` Activity left is `(1)/((2)^(14)` times the initial
`rArr (1)/((2)^14) xx 1 "curie" = (1)/(16384) xx 1 "curie" ~=`
`~~ 61 xx 10^-6 "curie" ~~ 60 mu "curie"`.