In hydrogen spectrum, the shortest wavelengths of Lyman and Balmer series are $\lambda_1$ and $\lambda_2$…

In hydrogen spectrum, the shortest wavelengths of Lyman and Balmer series are $\lambda_1$ and $\lambda_2$ respectively. The Rydberg constant of hydrogen is
  1. $\frac{\lambda_1+\lambda_2}{2}$
  2. $\frac{4\left(\lambda_2-\lambda_1\right)}{3 \lambda_1 \lambda_2}$
  3. $\frac{3\left(\lambda_2-\lambda_1\right)}{4 \lambda_1 \lambda_2}$
  4. $\frac{2\left(\lambda_2-\lambda_1\right)}{3 \lambda_1 \lambda_2}$

Solution

For Lymen series $\begin{aligned} & \frac{1}{\lambda_1}=\mathrm{R}_{\mathrm{H}}\left[\frac{1}{\mathrm{n}_1^2}-\frac{1}{\mathrm{n}_2^2}\right] \\ & \mathrm{n}_1=1 \text { and } \mathrm{n}_2=\infty\end{aligned}$ $\frac{1}{\lambda_1}=\mathrm{R}_{\mathrm{H}}$ ...(1) For balmer series $\begin{aligned} & \frac{1}{\lambda_2}=\mathrm{R}_{\mathrm{H}}\left[\frac{1}{\mathrm{n}_1^2}-\frac{1}{\mathrm{n}_2^2}\right] \\ & \mathrm{n}_1=2 \text { and } \mathrm{n}_2=\infty\end{aligned}$ $\frac{1}{\lambda_2}=\frac{\mathrm{R}_{\mathrm{H}}}{4}$ ...(2) $\begin{aligned} & \frac{1}{\lambda_2}-\frac{1}{\lambda_1}=\frac{\mathrm{R}_{\mathrm{H}}}{4}-\mathrm{R}_{\mathrm{H}} \\ & \frac{\lambda_1-\lambda_2}{\lambda_1 \lambda_2}=\frac{-3 \mathrm{R}_{\mathrm{H}}}{4}\end{aligned}$ Rydberg constant, $\mathrm{R}_{\mathrm{H}}=\frac{4\left(\lambda_2-\lambda_1\right)}{3 \lambda_1 \lambda_2}$

Asked in: AP EAMCET 2023 (17 May Shift 2)

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