Question

The decay constant of the parent nuclide in uranium series is $/lambda$. Then the decay constant for the stable end product of the series will be ?

• A. $\lambda$ / 238
• B. $\lambda$ / 206
• C. $\lambda$ / 208
• D. zero

Answer 1

The correct option is A $\lambda$ / 238

Decay constant $\lambda =\frac{1}{T}$, where $T$ is time taken by initial amount to fall to $\frac{1}{e}$ of its initial amount.

$\text{As a stable nuclei will NOT decay at all so time taken to fall to 1/e of its initial value will be}\infty$ whose inverse is $zero$ i.e $\lambda =0$ for stable nuclei.

Option D is correct.