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CET Karnataka Medical CET - Karnataka Medical Solved Paper-2011

  • question_answer
    The photoelectric threshold wavelength for silver is \[{{\lambda }_{0}}.\]The energy of the electron ejected from the surface of silver by an incident wavelength \[\lambda \left( \lambda <{{\lambda }_{0}} \right)\]will be

    A)  \[hc\left( {{\lambda }_{0}}-\lambda  \right)\]

    B)  \[\frac{hc}{{{\lambda }_{0}}-\lambda }\]

    C)  \[\frac{h}{c}\left( \frac{{{\lambda }_{0}}-\lambda }{\lambda {{\lambda }_{0}}} \right)\]

    D)  \[hc\left( \frac{{{\lambda }_{0}}-\lambda }{\lambda {{\lambda }_{0}}} \right)\]

    Correct Answer: D

    Solution :

    \[E=W+KE\] \[KE=E-W\] \[=\frac{hc}{\lambda }-\frac{hc}{{{\lambda }_{0}}}\] \[=hc\left[ \frac{1}{\lambda }-\frac{1}{{{\lambda }_{0}}} \right]=hc\left[ \frac{{{\lambda }_{0}}-{{\lambda }_{0}}}{\lambda \,{{\lambda }_{0}}} \right]\]


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