Radioactivity of a certain radioactive elements drops to frac{1}{64} of its initial value in 30 seco

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13.Nuclei

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The radioactivity of a certain radioactive elements drops to $\frac{1}{64}$ of its initial value in $30$ seconds. Its half life is ............. seconds

A

$8$

B

$15$

C

$7.5$

D

$5$

Solution

(d)

$\frac{N}{N_0}=\left(\frac{1}{2}\right)^n$

$\frac{1}{64}=\left(\frac{1}{2}\right)^n$

$n=6$

Hence half life is $5$ seconds

Standard 12

Physics

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