NEET NEET SOLVED PAPER 2017

  • question_answer
    The photoelectric threshold wavelength of silver is\[3250\times {{10}^{-10}}m.\]The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength \[2536\times {{10}^{-10}}m\]is                                     (Given \[h=4.14\times {{10}^{-15}}eVs\]and\[c=3\times {{180}^{8}}\,m{{s}^{-1}}\])

    A)  \[\approx 0.3\times {{10}^{6}}\,m{{s}^{-1}}\]   

    B) \[\approx 6\times {{10}^{5}}\,m{{s}^{-1}}\]

    C) \[\approx 0.6\times {{10}^{6}}\,m{{s}^{-1}}\]

    D) \[\approx 61\times {{10}^{3}}\,m{{s}^{-1}}\]

    Correct Answer: B , C

    Solution :

                    \[{{\lambda }_{0}}=3250\times {{10}^{-10}}\,m\]                 \[\lambda =2536\times {{10}^{-10}}\,m\]                 \[\text{o }\!\!|\!\!\text{ =}\frac{1242\,eV-nm}{325\,nm}=3.82\,eV\]                 \[hv=\frac{1242\,eV-nm}{253.6\,nm}=4.89\,eV\]                 \[K{{E}_{\max }}=(4.89-3.82)\,eV=1.077\,eV\]                                 \[\frac{1}{2}m{{v}^{2}}=1.077\times 1.6\times {{10}^{-19}}\]                                 \[v=\sqrt{\frac{2\times 1.077\times 1.6\times {{10}^{-19}}}{9.1\times {{10}^{-31}}}}\]                                 \[v=0.6\times {{10}^{6}}\,m/s\]

    Solution :

    \[{{\lambda }_{0}}=3250\times {{10}^{-10}}\,m\] \[\lambda =2536\times {{10}^{-10}}\,m\] \[\text{o }\!\!|\!\!\text{ =}\frac{1242\,eV-nm}{325\,nm}=3.82\,eV\] \[hv=\frac{1242\,eV-nm}{253.6\,nm}=4.89\,eV\] \[K{{E}_{\max }}=(4.89-3.82)\,eV=1.077\,eV\] \[\frac{1}{2}m{{v}^{2}}=1.077\times 1.6\times {{10}^{-19}}\] \[v=\sqrt{\frac{2\times 1.077\times 1.6\times {{10}^{-19}}}{9.1\times {{10}^{-31}}}}\] \[v=0.6\times {{10}^{6}}\,m/s\]


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