A sample of radioactive element has a mass of 10, gm at an instant t = 0 .approximate mass of this e

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13.Nuclei

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A sample of radioactive element has a mass of $10\, gm$ at an instant $t = 0$.The approximate mass of this element in the sample after two mean lives is ..........$gm$

A

$2.50 $

B

$3.70$

C

$6.30 $

D

$1.35$

(AIPMT-2003)

Solution

(d) $M = {M_0}{e^{ – \lambda t}};$ given $t = 2\left( {\frac{1}{\lambda }} \right)$

$ \Rightarrow M = 10{e^{ – \lambda \left( {\frac{2}{\lambda }} \right)}} = 10{\left( {\frac{1}{e}} \right)^2} $

$\Rightarrow M = 1.35\;gm$

Standard 12

Physics

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