Question

Two radioactive `X_(1)` and `X_(2)` have decay constants `10 lambda ` and `lambda` respectively . If initially they have the same number of nuclei, then the ratio of the number of nuclei of `X_(1)` to that of `X_(2)`will be `1//e` after a time .

Answer 1

Correct Answer - A::B::D
`(N_(x_1)(t))/(N_(x_2)(t))=1/e`
or `(N_0e^(-10lambdat))/(N_0e^(-lambdat)) = 1/e` (Initially, both have same number of nuclei say N `_(0)`)
or `e^(-9lambdat)=e^-1` or `e=e^(9lambdat)`
or `9lambdat = 1` or `t=1/(9lambda)`
:. The correct option is (d).