If $'f^{\prime}$ denotes the ratio of the number of nuclei decayed $\left(N_{d}\right)$ to the number of nuclei at $t=0$ $\left({N}_{0}\right)$ then for a collection of radioactive nuclei, the rate of change of $'f'$ with respect to time is given as:

$[\lambda$ is the radioactive decay constant]

  • [JEE MAIN 2021]
  • A

    $\lambda\left(1-{e}^{-\lambda t}\right)$

  • B

    $-\lambda e^{-\lambda t}$

  • C

    $\lambda e^{-\lambda t}$

  • D

    $-\lambda\left(1-{e}^{-\lambda . t}\right)$

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