Question 5: Atoms & Nuclei

Question

The half-life of a radioactive substance is $$20 \mathrm{~min}$$. The approximate time interval $$\left(t_2-t_1\right)$$ between the time $$t_2$$, when $$\frac{2}{3}$$ of it has decayed and time $$t_1$$ when $$\frac{1}{3}$$ of it had decayed is

Accepted Answer

$$\begin{aligned}
& 	ext { } 	herefore N_1=N_0-\frac{1}{3} N_0=\frac{2}{3} N_0 \
& 	ext { and } \quad N_2=N_0-\frac{2}{3} N_0=\frac{1}{3} N_0 \
& 	herefore \quad \frac{N_2}{N_1}=\left(\frac{1}{2}ight)^n \Rightarrow n=1 \
& 	herefore t_2-t_1=	ext { one half-life }=20 \mathrm{~min}
\end{aligned}$$

Answer

14 min

Answer

20 min

Answer

28 min

Answer

7 min

Atoms & Nuclei

The half-life of a radioactive substance is $20 \mathrm{~min}. The approximate time interval \left(t_2-t_1\right) between the time t_2, when \frac{2}{3} of it has decayed and time t_1 when \frac{1}{3}$ of it had decayed is

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