Question

A radioactive substance emits $100$ beta particles in the first $2$ seconds and $50$ beta particles in the next $2$ seconds. The mean life of the sample is

• A. $4$ seconds
• B. $2$ seconds
• C. $\frac{2}{0.693}$ seconds
• D. $2\times 0.693$ seconds

Answer 1

Answer: (C)

$\frac{2}{0.693}$ seconds

Answer 2

Given, In $1\,st$ two seconds $100 \beta$ partieles ?nd in next two seconds $50 \beta$ particles are emitted
$\therefore T_{1 / 2}=2 \,s$
Hence, $T_{m}=\frac{T_{1 / 2}}{0.693}=\frac{2}{0.693}$