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  • The activity of a radioactive material is . If the half life of the material is

The activity of a radioactive material is 2.56 \times 10^{-3} \mathrm{Ci}. If the half life of the material is 5 days, after how many days the activity will become 2 \times 10^{-5} \mathrm{Ci} ?

 

Option: 1

\mathrm{30\: days}


Option: 2

\mathrm{35\, days}


Option: 3

\mathrm{40\: days}


Option: 4

\mathrm{25\: days}


Answers (1)

best_answer

\mathrm{A=A_{0}\; e}^{\mathrm{-\lambda t}}

\mathrm{2 \times 10^{-5}=2.56 \times 10^{-3} \times e^{-\lambda t}}

\mathrm{\bar{e}^{\lambda t}=\frac{1}{128}=\left[\frac{1}{2}\right]^{+7}=\frac{A}{A_{0}}}

\mathrm{time\; taken=7\; half-life}

                         \mathrm{=7\times5}

                         \mathrm{=35\; days}

Hence, the correct answer is Option (2)

Posted by

sudhir.kumar

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