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JEE Mains · Physics · STD 12 - Dual nature of radiation and matter
  • JEE Mains 2023
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  • MCQ

Electron beam used in an electron microscope, when accelerated by a voltage of \(20\,kV\). has a de-Broglie wavelength of \(\lambda_0\). If the voltage is increased to \(40\,kV\). then the de-Broglie wavelength associated with the electron beam would be:

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Correct Answer

(D) \(\frac{\lambda_0}{\sqrt{2}}\)

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Detailed explanation

When electron is accelerated through potential difference \(V\), then

\(\text { K.E. }= eV\)

\(\Rightarrow \lambda=\frac{ h }{\sqrt{2 m ( KE )}}=\frac{ h }{\sqrt{2 meV }}\)

\(\therefore \quad \lambda \propto \frac{1}{\sqrt{ V }}\)

\(\therefore \quad \frac{\lambda}{\lambda_0}=\sqrt{\frac{20}{40}}\)

\(\therefore \quad \lambda=\frac{\lambda_0}{\sqrt{2}}\)

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