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13. Nuclei — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics13. Nuclei1 Mark
MCQ
For a certain radioactive process the graph between $In\, {R}$ and ${t}\,({sec})$ is obtained as shown in the figure. Then the value of half life for the unknown radioactive material is approximately $....\,{sec}.$
  • A
    $6.93$
  • ✓
    $4.62$
  • C
    $2.62$
  • D
    $9.15$
✓

Answer

Correct option: B.
$4.62$
b
${R}=R_{o} e^{-\lambda t}$

$\ell n R=\ell n R_{o}-\lambda t$

$-\lambda$ is slope of straight line

$\lambda=\frac{3}{20}$

$t_{1 / 2}=\frac{\ell n 2}{\lambda}=4.62$

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