Which of the following spectral series is found in the visible region…

The correct answer is Option (2) → Balmer

Each spectral series of hydrogen is the set of lines emitted when the electron jumps from higher levels to one particular lower level \( n_f \). The lower this final level, the larger the energy gap and the shorter the wavelength.

    \( \displaystyle \frac{1}{\lambda} = R\left(\frac{1}{n_f^{2}} - \frac{1}{n_i^{2}}\right) \)

Option (1) Lyman — Incorrect. The Lyman series ends on \( n_f = 1 \); its photons have the largest energies and lie in the ultraviolet.

Option (2) Balmer — Correct. The Balmer series ends on \( n_f = 2 \); its lines (656 nm, 486 nm, 434 nm, 410 nm and so on) lie in the visible region.

Option (3) Paschen — Incorrect. The Paschen series ends on \( n_f = 3 \); the energy gaps are smaller, so its lines lie in the infrared.

Option (4) Pfund — Incorrect. The Pfund series ends on \( n_f = 5 \); its lines lie farther out in the infrared.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), but it is still in the CUET 2026 syllabus, so do not skip it.

NCERT (Pre-rationalised edition, 2022-23):
Spectral Series – “… In 1885, the first such series was observed by a Swedish school teacher Johann Jakob Balmer (1825–1898) in the visible region of the hydrogen spectrum. This series is called Balmer series (Fig. 12.6).”

Spectral Series – “… The Lyman series is in the ultraviolet, and the Paschen and Brackett series are in the infrared region.”