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Question: Answered & Verified by Expert
' $\lambda_1$ ' is the wavelength of series limit of Lyman series, ' $\lambda_2$ ' is the wavelength of the first line of Lyman series and ' $\lambda_3$ ' is the series limit of the Balmer series. Then the relation between ' $\lambda_1$ ' $\lambda_2$ and $\lambda_3$ is
PhysicsAtomic PhysicsMHT CETMHT CET 2021 (21 Sep Shift 1)
Options:
  • A $\frac{1}{\lambda_1}-\frac{1}{\lambda_2}=\frac{1}{\lambda_3}$
  • B $\frac{1}{\lambda_1}=\frac{1}{\lambda_2}-\frac{1}{\lambda_3}$
  • C $\lambda_2=\lambda_1+\lambda_3$
  • D $\lambda_1=\lambda_2+\lambda_3$
Solution:
2080 Upvotes Verified Answer
The correct answer is: $\frac{1}{\lambda_1}-\frac{1}{\lambda_2}=\frac{1}{\lambda_3}$
Series limit of Lyman series is given by
$$
\frac{1}{\lambda_1}=\mathrm{R}\left(\frac{1}{1}-\frac{1}{\infty}\right)=\mathrm{R}
$$
Series limit of Balmer series given by
$$
\frac{1}{\lambda_3}=\mathrm{R}\left(\frac{1}{4}-\frac{1}{\infty}\right)=\frac{\mathrm{R}}{4}
$$
First line of Lyman series is given by
$$
\begin{aligned}
& \frac{1}{\lambda_2}=\mathrm{R}\left(\frac{1}{1}-\frac{1}{4}\right)=\mathrm{R}-\frac{\mathrm{R}}{4}=\frac{1}{\lambda_1}-\frac{1}{\lambda_3} \\
& \therefore \frac{1}{\lambda_1}-\frac{1}{\lambda_2}=\frac{1}{\lambda_3}
\end{aligned}
$$

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