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%
Verified Correct Answer: C.
Physical Principles & Numerical Solution
After 5 half-lives, the fraction of any radio-active substance left = (1/2)5 = 1/32
Thus the percentage of the original nuclei = 1/32/1 x 100/1
assuming the original amount is unity percentage left
= 1/32 x 100/1 = 3.12 = 3%
Source: Myschool Past Questions Archive (Record #12256)