In a mean life of a radioactive sample

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13.Nuclei

medium

In a mean life of a radioactive sample

A

About $1/3$ of substance disintegrates

B

About $2/3$ of the substance disintegrates

C

About $90\%$ of the substance disintegrates

D

Almost all the substance disintegrates

Solution

(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}$

Standard 12

Physics

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