The graph in figure shows how the count-rate $A$ of a radioactive source as measured by a Geiger counter varies with time $t.$ The relationship between $A$ and $t$ is : $($ Assume $ln\,\, 12 = 2.6)$

814-120

  • A

    $A = 2.6 \,e^{-10t}$

  • B

    $A = 12 \,e^{-10t}$

  • C

    $A = 2.6 \,e^{-0.1t}$

  • D

    $A = 1.2 \,e^{-0.1t}$

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