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Question: Two radioactive materials X<sub>1</sub> and X<sub>2</sub> contain same number of nuclei. If 6ls<sup>...

Two radioactive materials X1 and X2 contain same number of nuclei. If 6ls–1 and 4ls–1 are the decay constants of X1 and X2 respectively. The ratio of number of nuclei undecayed of X1 to that of X2 will be (1/e) after a time-

A

12λ\frac{1}{2\lambda}sec

B

110λ\frac{1}{10\lambda}sec

C

15λ\frac{1}{5\lambda} sec

D

1λ\frac{1}{\lambda}sec

Answer

12λ\frac{1}{2\lambda}sec

Explanation

Solution

N1 = N0 e–6lt, N2 = N0e–4lt

= or e–1 = e– 2lt or t = 12λ\frac { 1 } { 2 \lambda }