A radioactive species A of half-life T decays to stable species B. At t = 0 no B is present. At time t, let N₁ be the number of A nuclei and N₂ the number of B nuclei. If N₂/N₁ = 0.3, find t.
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Question

A radioactive species A of half-life T decays to stable species B. At t = 0 no B is present. At time t, let N₁ be the number of A nuclei and N₂ the number of B nuclei. If N₂/N₁ = 0.3, find t.

G1 Physics · Accepted Answer

N₁ = N₀·2⁻ᵗᐟᵀ and N₂ = N₀ − N₁. Given N₂/N₁ = 0.3, N₀/N₁ = 1.3. Hence 2ᵗᐟᵀ = 1.3 and t = T·log(1.3)/log2. Correct answer: D.