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13.Nuclei
medium
The half life of polonium is $140\, days$. After how many days, $16 \,gm$ polonium will be reduced to $1 \,gm$ .........$days$(or $15\,g$ will decay)
A
$700$
B
$280 $
C
$560 $
D
$420$
Solution
(c) $\frac{N}{{{N_0}}} = {\left( {\frac{1}{2}} \right)^{t/140}} $
$\Rightarrow \frac{1}{{16}} = {\left( {\frac{1}{2}} \right)^{t/140}}.$
$ \Rightarrow \frac{t}{{140}} = 4 \Rightarrow t = 560\;days$
Standard 12
Physics
