Engineering Entrance Exams
Two radioactive substances A and B have decay constants 5? and ? respectively. At t = 0, they have the
same number of nuclei. The ratio of number of nuclei of A to that of B will be (1/e)2
after a time interval
of
A.
1
?
B.
1
2?
C.
1
3?
D.
1
4?