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

  • question_answer
    The wavelength \[{{\lambda }_{e}}\] of an electron and \[{{\lambda }_{p}}\] of a photon of same energy E are related by                                                                                                                                                [NEET 2013]

    A)  \[{{\lambda }_{p}}\propto \lambda _{e}^{2}\] 

    B)  \[{{\lambda }_{p}}\propto {{\lambda }_{e}}\]

    C)  \[{{\lambda }_{p}}\propto \sqrt{{{\lambda }_{e}}}\]     

    D)       \[{{\lambda }_{p}}\propto \frac{1}{\sqrt{{{\lambda }_{e}}}}\]

    Correct Answer: A

    Solution :

    [a] Wavelength of electron,
    \[{{\lambda }_{e}}=\frac{h}{\sqrt{2mE}}\]
                and proton \[{{\lambda }_{p}}=\frac{hc}{E}\]
                \[\Rightarrow \]   \[\lambda _{e}^{2}=\frac{{{h}^{2}}}{2mE}\]
    or         \[E=\frac{hc}{{{\lambda }_{p}}}\]
    \[\therefore \]      \[\lambda _{e}^{2}=\frac{{{h}^{2}}}{2m.\frac{hc}{{{\lambda }_{p}}}}\]
    \[\Rightarrow \]   \[\lambda _{e}^{2}=\frac{{{h}_{2}}}{2mhc}{{\lambda }_{p}}\]
    \[\Rightarrow \]   \[\lambda _{e}^{2}\propto {{\lambda }_{p}}\]


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