JEE Main & Advanced Sample Paper JEE Main Sample Paper-44

  • question_answer
    The work functions for metal A,B and C are 1.92 eV, 2.0 eV and 5 eV respectively. According to Einstein's equation, the metals which will emit photoelectrons for a radiation of wavelength \[4000\,\overset{\text{o}}{\mathop{\text{A}}}\,\]is/are

    A)  only A                                  

    B)  A and B

    C)  All the three metals                  

    D)  None of these

    Correct Answer: B

    Solution :

     \[E=\frac{hc}{\lambda }=\frac{6.63\times {{10}^{-34}}\times 3\times {{10}^{8}}}{41\times {{10}^{-8}}}J\]\[=\frac{19.89\times {{10}^{-18}}}{41\times 1.6\times {{10}^{-19}}}eV=3.0\,eV\] For metals A and B, the work function is less than 3.0 eV, so photoelectrons from metals A and B will be emitted with radiation of \[4000\,\overset{o}{\mathop{\text{A}}}\,\].


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