Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be :-
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Question

Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be :-

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G1 Physics · Accepted Answer

Step 1: Use N(t) = N₀ exp(−λt), A = λN and T₁/₂ = ln2/λ. Step 2: For two samples, write the decay law separately and equate the required activities/numbers. Final: A: 5 : 4.