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13.Nuclei
medium
If half-life of a substance is $3.8\, days$ and its quantity is $10.38\, gm$. Then substance quantity remaining left after $19\, days$ will be ........$gm$
A
$0.151$
B
$0.32 $
C
$1.51$
D
$0.16$
Solution
(b) Number of half lives $n = \frac{{19}}{{3.8}} = 5;$
Now $\frac{N}{{{N_0}}} = {\left( {\frac{1}{2}} \right)^n}$
$ \Rightarrow \frac{N}{{10.38}} = {\left( {\frac{1}{2}} \right)^5}$
$\Rightarrow N = 10.38 \times {\left( {\frac{1}{2}} \right)^5}$$ = 0.32\,gm$
Standard 12
Physics
