MCQ
$99\%$ of a radioactive element will decay between
- ✓$6$ and $7$ half lives
- B$7 $ and $8 $ half lives
- C$8$ and $9$ half lives
- D$9$ half lives
✓
Answer
Correct option: A.
$6$ and $7$ half lives
a
(a) $N = {N_0}{\left( {\frac{1}{2}} \right)^n} $
(a) $N = {N_0}{\left( {\frac{1}{2}} \right)^n} $
$\Rightarrow \frac{N}{{{N_0}}} = {\left( {\frac{1}{2}} \right)^n}$
$ \Rightarrow \frac{1}{{100}} = {\left( {\frac{1}{2}} \right)^n}$
$\Rightarrow {2^n} = 100$
$n$ comes out in between $6$ and $7.$
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