MCQ
In a mean life of a radioactive sample
- AAbout $1/3$ of substance disintegrates
- ✓About $2/3$ of the substance disintegrates
- CAbout $90\%$ of the substance disintegrates
- DAlmost all the substance disintegrates
✓
Answer
Correct option: B.
About $2/3$ of the substance disintegrates
b
(b) By using $N = {N_0}{e^{ - \lambda t}}$ and $t = \tau = \frac{1}{\lambda }$
(b) By using $N = {N_0}{e^{ - \lambda t}}$ and $t = \tau = \frac{1}{\lambda }$
Substance remains $ = N = \frac{{{N_0}}}{e} = 0.37{N_0}\simeq \,\frac{{{N_0}}}{3}$
$\therefore$ Substance disintegrated $ = {N_0} - \frac{{{N_0}}}{3} = \frac{{2{N_0}}}{3}$
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