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JEE Main 2025 (7 Apr, Shift 1) · Hydrogen Spectrum & Spectral Series

Hydrogen Spectrum & Spectral Series question from JEE Main 2025 (7 Apr, Shift 1)

Q11JEE Main 2025 · 7 APR · SHIFT 1Easy

Hydrogen Spectrum & Spectral Series

For a hydrogen atom, the ratio of the largest wavelength of Lyman series to that of the Balmer series is

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Answer: (a)

  1. Largest wavelength = first line.
  2. Lyman (2→12 \to 1): 1λL=R(1−14)=3R4\frac{1}{\lambda_L} = R\left(1 - \frac{1}{4}\right) = \frac{3R}{4}, so λL=43R\lambda_L = \frac{4}{3R}.
  3. Balmer (3→23 \to 2): 1λB=R(14−19)=5R36\frac{1}{\lambda_B} = R\left(\frac{1}{4} - \frac{1}{9}\right) = \frac{5R}{36}, so λB=365R\lambda_B = \frac{36}{5R}.
  4. λLλB=43×536=527\frac{\lambda_L}{\lambda_B} = \frac{4}{3} \times \frac{5}{36} = \frac{5}{27}.
  5. So the answer is (a) 5:275 : 27.
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