Question

The half life of ${}^{58}$Co is $72$days. The time taken for $\frac{3}{4}th$ of the initial mass to disintegrate is:

• A. $144days$
• B. $235days$
• C. $344days$
• D. $433days$

Answer 1

Answer: (A)

$144days$

$t_{1/2}=72days$

Initial $=N_0$

$left=\frac{N}{4}$

i.e. Time is lapsed by $2t_{1/2}$

$\therefore 2t_{1/2}=144days$