NEET 2016 Phase 1 · PhysicsSpectral seriesPrevious Year Question
Given the value of Rydberg constant is 10⁷ m⁻¹, the wave number of the last line of the Balmer series in hydrogen spectrum will be:
Answer: (C) 0.25 × 10⁷ m⁻¹. Answer: (c) 0.25 × 10⁷ m⁻¹ Solution: The 'last line' of the Balmer series is the series limit, transition n=∞ → n=2.
- A.0.025 × 10⁴ m⁻¹
- B.0.5 × 10⁷ m⁻¹
- C.0.25 × 10⁷ m⁻¹✓
- D.2.5 × 10⁷ m⁻¹
Correct Answer
(C) 0.25 × 10⁷ m⁻¹
Solution & Explanation
Answer: (c) 0.25 × 10⁷ m⁻¹ Solution: The 'last line' of the Balmer series is the series limit, transition n=∞ → n=2. Wave number 1/λ = RZ²(1/n₁² − 1/n₂²) = R(1/2² − 1/∞²) = R/4. With R = 10⁷ m⁻¹: 1/λ = 10⁷/4 = 0.25 × 10⁷ m⁻¹.
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