Half - lives of two radioactive . Initially . The samples have equal number of nuclie After `80` minutes ,the ratio of decyed number of `A and B` nuclei will be

Answer

1.25

Explanation

Half-life of `A, T_(1//2(A)) = 20 "min"`
Half-life of `B, T_(1//2(B)) = 40 "min"`
Initially, number of nuclei in each sample = N
Now, 80 min `4T_(1//2(A)) = 2T_(1//2(B))`
`N_A = N/(2^4) = N/16 , N_B = N/(2^2) = N/4`
`:.` Number of decayed nuclei of `A = N - N_A = 15/16 N`
`:.`Number of decayed nuclei of `B = N - N_(B) = 3/2N " " :.` Required ratio `= (16/3 N)/(3/4 N) = 5/4`.