Radioactive material 'A' has decay constant '8λ' and material 'B' has decay constant 'λ'. Initially they have the same number of nuclei. After what time, the ratio of the number of nuclei of material 'B' to that of 'A' will be 1?

NA = NA0e-8λt
NB = NB0e-λt
NA0 = NB0
=> NB/NA = e-λt/e-8λt = e7λt = 1
=> 7λt = 0
t = 0 (This is incorrect, there must be a mistake in the provided solution.)
Let's re-examine the problem. We want to find t when NB/NA = 1.
NB/NA = (NB0e-λt) / (NA0e-8λt) = e7λt
If NB/NA = 1, then e7λt = 1. This implies 7λt = 0, which means t=0. However, this is not a useful solution. It seems there's an error in the original solution provided. The question likely intended to ask for a ratio other than 1 or there is an issue with the given solution.