JEE Main & Advanced Sample Paper JEE Main - Mock Test - 28

  • question_answer
    If the radius of first orbit of H-atom is do, then de-Broglie wavelength of electron in 4th orbit is

    A) \[2\pi {{a}_{0}}\]                     

    B) \[16{{a}_{0}}\]

    C) \[{{a}_{0}}/4\]

    D) \[8\pi {{a}_{0}}\]

    Correct Answer: D

    Solution :

    [d]: \[{{r}_{n}}={{a}_{0}}\times {{n}^{2}},{{r}_{4}}={{a}_{0}}\times {{4}^{2}}=16{{a}_{0}}\] \[mv=4\times \frac{h}{2\pi {{r}_{4}}}=\frac{4h}{2\pi \times 16{{a}_{0}}}=\frac{h}{8\pi {{a}_{0}}}\] \[\therefore \]\[\lambda =\frac{h}{mv}=8\pi {{a}_{0}}\]


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