The percentage of the original nuclei of the sample of a radioactive substance left after 5 half – lives is
-
A.
8% -
B.
5% -
C.
3% -
D.
1%
Correct Answer: Option C
Explanation
After 5 half-lives, the fraction of any radio-active substance left = (1/2)5 = 1/32
Thus the percentage of the original nuclie = 1/32/1 x 100/1
assuming the original amount is unity percentage left
= 1/32 x 1400/1 = 3.12