CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2008

  • question_answer
    The ratio of minimum wavelengths of Lyman and Balmer series will be

    A)  1.25                                      

    B)  0.25

    C)  5                                            

    D)  10

    Correct Answer: B

    Solution :

    The series end of Lyman series corresponds to transition from \[{{n}_{i}}=\infty \] to \[{{n}_{f}}=1\], corresponding to the wavelength                 \[{{({{\lambda }_{\min }})}_{L}}=R\left[ \frac{1}{1}-\frac{1}{\infty } \right]=R\] \[\Rightarrow \]               \[{{({{\lambda }_{\min }})}_{L}}=\frac{1}{R}=912\,\overset{o}{\mathop{A}}\,\]                  ... (i) For last line of Balmer series                 \[\frac{1}{{{({{\lambda }_{\min }})}_{B}}}=R\left[ \frac{1}{{{(2)}^{2}}}-\frac{1}{{{(\infty )}^{2}}} \right]=\frac{R}{4}\] \[\Rightarrow \]               \[{{({{\lambda }_{\min }})}_{B}}=\frac{4}{R}=3636\,\overset{o}{\mathop{A}}\,\]                               ... (ii) Dividing Eq. (i) by Eq. (ii), we get                 \[\frac{{{({{\lambda }_{\min }})}_{L}}}{{{({{\lambda }_{\min }})}_{B}}}=0.25\]


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