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NEET Physics Atomic Physics NEET PYQ-Atomic Physics

  • question_answer
    The electron in the hydrogen atom jumps from excited state \[(n=3)\] to its ground state \[(n=1)\] and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron in nth state \[{{E}_{n}}=-\frac{13.6}{{{n}^{2}}}eV\])           [AIPMT (M) 2010]

    A)  5.1 V     

    B)  12.1 V

    C)  17.2 V      

    D)    7 V

    Correct Answer: D

    Solution :

    For \[n=1,{{E}_{1}}=-\frac{13.6}{{{(1)}^{2}}}=-13.6\,eV\]
    and for \[n=3,{{E}_{3}}=-\frac{13.6}{{{(3)}^{2}}}=-1.51\,eV\]
    So, required energy
    \[E={{E}_{3}}-{{E}_{1}}=-(1.51)-(-13.6)\]
    \[=12.09\,eV\]
    \[\because \]       \[E=W+eV\]
    \[\therefore \]      \[eV=E-W\]
    \[eV=(12.09-5.1)e\]
    \[V=7\,volt\]


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