Question

If $3/4$ quantity of radioactive substance disintegrates in $2$ hours, its half life period will be:

• A. $15$ minutes
• B. $30$ minutes
• C. $60$ minutes
• D. $90$ minutes

Answer 1

The correct option is C $60$ minutes

$\lambda =\frac{1}{120}ln\left(\frac{N_o}{N_o-N}\right)$

$N=\frac{3}{4}{N}_o$

$\lambda =\frac{ln2}{60}$

$t_{half}=\frac{ln2}{\lambda }$

$=\frac{ln2\times 60}{ln2}$

$=60min$