Answer: n=2.
- A n=1
- B n=2
- C n=3
- D n=4
Correct answer: B. n=2
Explanation: Balmer series: electrons fall to n=2. These transitions produce visible light (H-alpha, H-beta, etc.).

The Geiger–Marsden alpha-scattering result: a few alpha particles bounce back at large angles, which rules out Thomson’s diffuse model and demands a tiny, massive, positively charged nucleus. Image: Kurzon, CC BY 3.0, via Wikimedia Commons.
Concept context
Thomson's plum-pudding model, Rutherford's nuclear model from alpha-scattering, Bohr's postulates and hydrogen spectrum, spectral series (Lyman to Pfund), Rydberg formula, and limitations of each model.