# NEET Physics Nuclei Questions Solved

The half life of ${}^{131}\mathrm{I}$ is 8 days. Given a sample of ${}^{131}\mathrm{I}$ at time t = 0, we can assert that
(a) No nucleus will decay before t = 4 days
(b) No nucleus will decay before t = 8 days
(c) All nuclei will decay before t = 16 days
(d) A given nucleus may decay at any time after t = 0

(d) Number of nuclei decreases exponentially
$\mathrm{N}={\mathrm{N}}_{0}{\mathrm{e}}^{-\mathrm{\lambda t}}$  and Rate of decay $\left(-\frac{\mathrm{dN}}{\mathrm{dt}}\right)=\mathrm{\lambda N}$
Therefore, decay process losts up to t = $\infty$.
Therefore, a given nucleus may decay at any time after t = 0.

Difficulty Level:

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