Q152 / 180 · COMEDK 2023 (Memory Based) · Physics

The first emission of hydrogen atomic spectrum in Lyman series appears at a wavelength of

  • A
    $\frac{3 R}{4} \mathrm{~cm}^{-1}$
  • Correct answer
    B
    $\frac{4}{3 R} \mathrm{~cm}$
  • C
    $\frac{7 R}{144} \mathrm{~cm}^{-1}$
  • D
    $\frac{400}{9 R} \mathrm{~cm}$

Solution

$\begin{aligned} & \text { We know that, } \frac{1}{\lambda}=R\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right) \\ & \Rightarrow \quad \frac{1}{\lambda}=R\left(\frac{1}{1_1^2}-\frac{1}{2^2}\right)=\frac{3 R}{4} \Rightarrow \lambda=\frac{4}{3 R} \mathrm{~cm}\end{aligned}$

Hence, the correct answer is option: 'B'.

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