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JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Photon and Photoelectric Effect

  • question_answer
    The work functions for sodium and copper are \[2eV\] and \[4eV\]. Which of them is suitable for a photocell with 4000 Å light                                                    [RPET 1999]

    A)            Copper                                   

    B)            Sodium

    C)            Both                                        

    D)            Neither of them

    Correct Answer: B

    Solution :

                       Threshold wavelength for Na, \[{{\lambda }_{Na}}=\frac{12375}{2}=6187.5{\AA}\]                    Also \[{{\lambda }_{Cu}}=\frac{12375}{4}=3093.75\]            Since \[{{\lambda }_{Na}}>4000{\AA}\]; So Na is suitable.


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