Physics

Problem

Two radioactive substances A and B have decay constants

5\lambda

and

\lambda

respectively. At

t=0

, a sample has the same number of the two nuclei. The time taken for the ratio of the number of nuclei to become

\left(\frac{1}{e}\right)^2

will be: a.

1/2\lambda

1/4\lambda

1/\lambda

2/\lambda