AMU Medical AMU Solved Paper-2009

  • question_answer
    Light of frequency 1015 Hz falls on a metal surface of work function 2.5 eV. The stopping potential of photoelectrons in volts is

    A)  1.6                                        

    B)  2.5

    C)  4.1                                        

    D)  6.6

    Correct Answer: A

    Solution :

                     Given, frequency of light \[={{10}^{15}}Hz\] Work function = 2.5 eV Now, wavelength of incident light                 \[\lambda =\frac{c}{v}=\frac{3\times {{10}^{8}}}{{{10}^{15}}}=3\times {{10}^{-7}}\]                 \[=3000\,\,\overset{o}{\mathop{A}}\,\] The energy of \[=3000\,\,\overset{o}{\mathop{A}}\,\] light                                                 \[=\frac{hc}{\lambda }\]                                                 \[=\frac{12400}{3000}=4.13\,eV\] \[\therefore \] Maximum kinetic energy of the electron                 \[=hv-W\] and        \[{{K}_{\max }}=e{{V}_{0}}\] \[\therefore \]  \[1.63\,eV\,=e{{V}_{0}}\] \[\Rightarrow \]               \[{{V}_{0}}=1.63\,V\]


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