Modern Physics Ques 133
- 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 …….
$(1983,2 M)$
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Answer:
Correct Answer: 133.($500$ dps,$125$ dps)
Solution:
Formula:
- $R=R _0 (\frac{1}{2})^{n}$
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} (\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} $
BETA
