Concept: In the hydrogen atom spectrum, the spectral series are strictly classified by the region of the electromagnetic spectrum in which their emitted photons fall, determined by the final resting shell (\( p \)).
Formula:$$ p=1 \rightarrow \text{UV (Lyman)} $$
$$ p=2 \rightarrow \text{Visible (Balmer)} $$
$$ p \ge 3 \rightarrow \text{IR (Paschen, Brackett, Pfund)} $$
Solution:- Lyman is Ultraviolet (UV). Balmer is Visible.
- Paschen (\( p=3 \)), Brackett (\( p=4 \)), and Pfund (\( p=5 \)) all feature low-energy transitions that fall squarely into the Infrared (IR) region.
- Option B correctly pairs two IR series. Option C also correctly pairs two IR series.
- Therefore, Option D accurately encapsulates all correct groupings.
Why other options are incorrect:Option A is entirely incorrect as it includes UV and Visible series. Options B and C are technically true but functionally incomplete individually compared to the overarching Option D.
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