Question

The half-life of ratio active element is $100\mu s$ . The time taken for the radioactivity of a sample to decay by $93.75\%$ of its initial value is :

• A. $400\mu s$
• B. $6.3\mu s$
• C. $40\mu s$
• D. $300\mu s$

Answer 1

Answer: (A)

$400\mu s$

Since $93.75\%$ of its initial value is decayed.

Remaining amount is $6.25\%$ i.e $\frac{1}{16}$ of initial value.

Time of decay$=4\times$ half life period$=4\times 100\mu s=400\mu s$