NEET Physics Photo Electric Effect, X- Rays & Matter Waves NEET PYQ-Photo Electric Effect,X-Rays

  • question_answer
    Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would                                                         [AIPMT (S) 2011]

    A)  decrease by 2 times

    B)       decrease by 4 times

    C)  increase by 4 times

    D)       increase by 2 times

    Correct Answer: A

    Solution :

    We have
                            \[\lambda =\frac{12.27}{\sqrt{V}}\]
    So,       \[\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\sqrt{\frac{{{V}_{2}}}{{{V}_{1}}}}\]
                            \[{{\lambda }_{2}}={{\lambda }_{1}}\sqrt{\frac{{{V}_{1}}}{{{V}_{2}}}}\]
                            \[{{\lambda }_{2}}={{\lambda }_{1}}\sqrt{\frac{25}{100}}\]
                            \[{{\lambda }_{2}}={{\lambda }_{1}}\sqrt{\frac{1}{4}}=\frac{{{\lambda }_{1}}}{2}\]


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