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NEET Physics Atomic Physics NEET PYQ-Atomic Physics

  • question_answer
    The total energy of an electron in the first excited state of hydrogen is about \[-3.4\text{ }eV\]. Its kinetic energy in this state is:                                                                                                           [AIPMT (S) 2005]

    A)  \[-3.4\text{ }eV\]

    B)                   \[-6.8\,eV\]

    C)  \[6.8\text{ }eV\]  

    D)             \[3.4\text{ }eV\]

    Correct Answer: C

    Solution :

    Key Idea: The kinetic energy is equal to the negative of total energy.
                Kinetic energy of electron
                            \[K=\frac{Z{{e}^{2}}}{8\pi {{\varepsilon }_{0}}r}\]
                Potential energy of electron
                            \[U=-\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Z{{e}^{2}}}{r}\]
                \[\therefore \]      Total energy
                            \[E=K+U=\frac{Z{{e}^{2}}}{8\pi {{\varepsilon }_{0}}r}-\frac{Z{{e}^{2}}}{4\pi {{\varepsilon }_{0}}r}\]
                or         \[E=-\frac{Z{{e}^{2}}}{8\pi {{\varepsilon }_{0}}r}\]
                or         \[E=-K\]


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