What is the wavelength of the line emitted when a hydrogen electron falls from n = 3 to n = 2 (R = 1.097 × 10⁷ m⁻¹)?
Correct answer B. 656 nm
Explanation
1/λ = R(1/2² − 1/3²) = 1.097 × 10⁷ × 5/36 = 1.524 × 10⁶ m⁻¹, so λ = 656 nm. 486 nm is the 4 → 2 line and 103 nm is 3 → 1.
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