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BCECE Engineering BCECE Engineering Solved Paper-2014

  • question_answer
    In photoelectric effect, if the energy required to overcome the attractive forces on the electron, (work functions) of Li, Na and Rb are\[\text{2}.\text{41 eV}\], \[\text{2}.\text{3}0\text{ eV}\] and \[\text{2}.0\text{9 eV}\] respectively, the work function of 'K' could approximately be in eV.

    A) 2.52                                       

    B) 2.20

    C) 2.35                                       

    D) 2.01

    Correct Answer: B

    Solution :

    As the size of atom (element) increases, energy required to overcome the attractive force on outermost electron decreases. Li. Na. K and Rb are the members of same group and have the following order of size \[\text{Li}<\text{Na}<\text{K}<\text{Rb}\] Thus, the energy in case of K is intermediate of Rb and Na,/.e., \[\text{2}.\text{3}0<\text{K}>\text{2}.0\text{9}\] or the energy for K is 2.20 \[\text{eV}\].


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