The half-life of a radioactive substance is 3 | vedclass

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Question

$N_{0}=$ Nuclei at time $t=0$

$N_{\mathrm{1}}=$ Remaining nuclei after $40 \%$ decay

$=(1-0.4) N_{0}=0.6 N_{0}$

$N_{2}=$ Remaining nuclei aft

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$N_{0}=$ Nuclei at time $t=0$

$N_{\mathrm{1}}=$ Remaining nuclei after $40 \%$ decay

$=(1-0.4) N_{0}=0.6 N_{0}$

$N_{2}=$ Remaining nuclei after $85 \%$ decay

$=(1-0.85) N_{0}=0.15 N_{0}$

$	herefore$  $\frac{N_{2}}{N_{1}}=\frac{0.15 N_{0}}{0.6 N_{0}}=\frac{1}{4}=\left(\frac{1}{2}ight)^{2}$

Hence, two half life is required between $40 \%$ decay and $85 \%$ decay of a radioactive substance.

$	herefore$ Time taken $=2 	au_{1 / 2}=2 	imes 30 \mathrm{min}=60 \mathrm{min}$

The half-life of a radioactive substance is $30$ minutes. The times (in minutes ) taken between $40\%$ decay and $85\%$ decay of the same radioactive substance is

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