Question
Question: Half-life of a radioactive substance A is two times the half-life of another radioactive substance B...
Half-life of a radioactive substance A is two times the half-life of another radioactive substance B. Initially the number of nuclei of A and B are NA and NB respectively. After three half lives of A number of nuclei of both are equal. Then the ratio NA/NB is
A
1/4
B
1/8
C
1/3
D
1/6
Answer
1/8
Explanation
Solution
Three half-lives of A is equivalent to six half-lives of B. Hence, NA(21)3= NB (21)6
or NBNA = 81