What is the half-life (in years) period of a radioactive material if its activity drops to $1 / 16^{\text {th }}$ of its initial value of $30$ years?

  • [JEE MAIN 2022]
  • A

    $9.5$

  • B

    $8.5$

  • C

    $7.5$

  • D

    $10.5$

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  • [JEE MAIN 2022]

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