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Nuclei — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsNuclei3 Marks
Question
  1. Define ‘activity’ of a radioactive substance.
  2. Two different radioactive elements with half lives $T_1$ and $T_2$ have $N_1$ and $N_2$ undecayed atoms respectively present at a given instant. Derive an expression for the ratio of their activities at this instant in terms of $\mathrm{N}_1$ and $\mathrm{N}_2$.
✓

Answer

  1. Number of radioactive nuclei decaying per second at any time.
  2. $R_1=\lambda_1N_1=\frac{0.693}{T_1}N_1$
$R_2=\lambda_2N_2=\frac{0.693}{T_2}N_2$

$\frac{R_1}{R_2}=\frac{N_1}{N_2}\times\frac{T_2}{T_1}$

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