Two different radioactive elements with half lives ' T₁ ' and ' T₂ ' have undecayed atoms ' N₁ ' and ' N₂ ' respectively present at a given instant. The ratio of their activities at that instant is (a) (N₁ T₁)/(N₂ T₂) (b) (N₂ T₂)/(N₁ T₁) (c) (N₁ T₂)/(N₂ T₁) (d) (N₁ N₂)/(T₁ T₂)

Answer: (c). Activity A = λ N = (0.693)/(T)N. (A₁)/(A₂) = (N₁/T₁)/(N₂/T₂) = (N₁T₂)/(N₂T₁). So the answer is (c) (N₁T₂)/(N₂T₁).

Two different radioactive elements with half lives ' T₁ ' and ' T₂ '… | MHT CET 2023 (12 May, Shift 2)

Q33MHT CET 2023 · 12 MAY · SHIFT 2Easy

Law of Radioactive Decay

Two different radioactive elements with half lives ' $\text{T}_1$ ' and ' $\text{T}_2$ ' have undecayed atoms ' $\text{N}_1$ ' and ' $\text{N}_2$ ' respectively present at a given instant. The ratio of their activities at that instant is

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Answer: (c)

Activity $A = \lambda N = \frac{0.693}{T}N$ .
$\frac{A_1}{A_2} = \frac{N_1/T_1}{N_2/T_2} = \frac{N_1T_2}{N_2T_1}$ .
So the answer is (c) $\frac{N_1T_2}{N_2T_1}$ .

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Law of Radioactive Decay question from MHT CET 2023 (12 May, Shift 2)

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