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NEET 2011 (AIPMT, Prelims) · Hydrogen Spectrum & Spectral Series

Hydrogen Spectrum & Spectral Series question from NEET 2011 (AIPMT, Prelims)

Q58NEET 2011 · AIPMT · PRELIMSMedium

Hydrogen Spectrum & Spectral Series

The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is

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Answer: (d)

  1. 1λ=RZ2(1n12−1n22)\frac{1}{\lambda} = RZ^2\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)
  2. H, Lyman first line (2→12 \to 1): 1λ=3R4\frac{1}{\lambda} = \frac{3R}{4}
  3. Ion, Balmer second line (4→24 \to 2): 1λ=RZ2⋅316\frac{1}{\lambda} = RZ^2\cdot\frac{3}{16}
  4. 3Z216=34⇒Z2=4⇒Z=2\frac{3Z^2}{16} = \frac{3}{4} \Rightarrow Z^2 = 4 \Rightarrow Z = 2
  5. So the answer is (d) 2.
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