Modern Physics 3 Question 33
34. The radioactive decay rate of a radioactive element is found to be $10^{3}$ disintegration/second at a certain time. If the half-life of the element is one second, the decay rate after one second is ……. and after three seconds is.
$(1983,2 M)$
Analytical & Descriptive Questions
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Solution:
- $R=R _0 \frac{1}{2}^{n}$
Here $R _0=$ initial activity $=1000$ disintegration $/ s$
and $\quad n=$ number of half-lives.
$$ \begin{aligned} & \text { At } \quad t=1 s, n=1 \\ & \therefore \quad R=10^{3} \quad \frac{1}{2}=500 \text { disintegration } / s \\ & \text { At } \quad t=3 s, n=3 \\ & R=10^{3} \frac{1}{2}^{3}=125 \text { disintegration } / s \end{aligned} $$
