13.Nuclei
medium

The half-life of radium is about $1600$ years. Of $100\, g$ of radium existing now, $25\, g$ will remain unchanged after .......... $years$

A

$2400$

B

$3200$ 

C

$4800$ 

D

$6400$ 

(AIPMT-2004)

Solution

(b) $M = {M_0}{\left( {\frac{1}{2}} \right)^{\frac{t}{{{T_{1/2}}}}}}$

$ \Rightarrow 25 = 100{\left( {\frac{1}{2}} \right)^{\frac{t}{{1600}}}}$

==> $t= 3200$ years.

Standard 12
Physics

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