JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Evening)

  • question_answer
    In a photoelectric experiment, the wavelength of the light incident on a metal is changed from 300 nm to 400 nm. The decrease in the stopping potential is close to\[\left( \frac{hc}{e}=1240nm-V \right)\] [JEE  Main Online Paper (Held on 11-jan-2019 Evening)]

    A) 2.0 V                          

    B) 0.5 V

    C) 1.0 V              

    D)   1.5 V

    Correct Answer: C

    Solution :

    \[{{E}_{1}}=\frac{1240eV-nm}{300}=4.13eV\] \[{{E}_{2}}=\frac{1240\,eV-nm}{400}=3.10\,eV\] \[{{K}_{{{\max }_{1}}}}={{E}_{1}}-{{\phi }_{0}},{{K}_{{{\max }_{2}}}}={{E}_{2}}-{{\phi }_{0}}\] \[{{K}_{{{\max }_{1}}}}-{{K}_{{{\max }_{2}}}}={{E}_{1}}-{{E}_{2}}=1.03eV\] \[{{V}_{1}}-{{V}_{2}}=1.03V\]                                   \[(\because K=eV)\]


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