CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2002

  • question_answer
    The de-Broglie wavelength  of an electron in the first Bohr orbit is:

    A)  equal to half the circumference of the first orbit

    B)  equal   to   one   fourth   the circumference of the first orbit

    C)  equal to the circumference of the first orbit

    D)  equal to twice the circumference of the first orbit

    Correct Answer: C

    Solution :

    de-Broglie wavelength \[\lambda =\frac{h}{p}\]                 \[\therefore \]  \[L=\frac{nh}{2\pi }\]for \[{{\text{H}}_{\text{2}}}\]atom (Bohr theory.) \[L=\]angular momentum \[n=\]principal quantum number \[\therefore \]  \[L=m\upsilon \,\,\,{{r}_{n}}=p{{r}_{n}}\]                 \[{{r}_{n}}=\]radius of orbit \[p{{r}_{n}}=\frac{hn}{2\pi }\]                                 \[\frac{h}{p}=\lambda \Rightarrow \frac{2\pi {{r}_{n}}}{n}\] for \[n=1\]first Bohr's orbit \[\lambda =2\pi \,{{r}_{1}}=\]circumference of first Bohr orbits.


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