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The Nucleus — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsThe Nucleus3 Marks
Question
$\text{ }^{197}_{80}\text{Hg}$ decay to $\text{ }^{197}_{79}\text{Au}$ through electron capture with a decay constant of 0.257 per day.
  1. What other particle or particles are emitted in the decay?
  2. Assume that the electron is captured from the K shell. Use Moseley's law $\sqrt{\text{v}}=\text{a(Z}-\text{b})$ with $\text{a}=4.95\times10^7\text{s}^{-\frac{1}{2}}$ and b = 1 to find the wavelength of the $\text{K}_{\alpha}$ X-ray emitted following the electron capture.
✓

Answer

  1. $\text{P + e}\rightarrow\text{n + v}$ neutrino $\big[\text{a}\rightarrow4.95\times10^7\text{s}^{-\frac{1}{2}};\text{b}\rightarrow1\big]$
  2. $\sqrt{\text{f}}=\text{a(z}-\text{b})$
$\Rightarrow\sqrt{\frac{\text{c}}{\lambda}}=4.95\times10^7(79-1)=4.95\times10^7\times78$

$\Rightarrow\frac{\text{c}}{\lambda}=(4.95\times78)^2\times10^{14}$

$\Rightarrow\lambda=\frac{3\times10^8}{14903.2\times10^{14}}$

$=2\times10^{-5}\times10^{-6}=2\times10^{-4}\text{m}=20\text{pm}$

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