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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 purpose ? [R H = 1 × 10 5 cm –1 , h = 6.6 × 10 –34 Js, c = 3 × 10 8 ms –1 ]

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

Correct answer: Paschen, ∞ → 3

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