Half lives of two radioactive nuclei A and B are 10 minutes and 20 minutes, respectively. If, initially a sample has equal number of nuclei, then after 60 minutes, the ratio of decayed numbers of nuclei A and B will be:

Step-by-step solution

Half-life of A : t 1 2 ( A ) = 10 minutes Number of half-lives in 60 minutes are: 60 10 = 6 ∴ Number of decayed nuclei of A N A = N o - N o 2 6 = 63 64 N o Similarly, Half-life of B : t 1 2 ( B ) = 20 minutes Number of half-lives of B in 60 minutes are: 60 20 = 3 ∴ Number of decayed nuclei of B N B = N o - N o 2 3 = 7 8 N o ∴ N A : N B = 63 64 : 7 8 = 9 : 8 = 9 : 8