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Heat treatment of muscular pain involves radiation of wavelength of about 900 nm. Which spectral line of H atom is suitable for this ? Given: Rydberg constant R H = 10 5 cm –1 , h = 6.6 × 10 –34 J s, c = 3 × 10 8 m/s)

1. Paschen series, ∞ → 3
2. Lyman series, ∞ → 1
3. Balmer series, ∞ → 2
4. Paschen series, 5 → 3

Correct answer: Paschen series, ∞ → 3

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