The wavenumber of the third line in the Lyman series of a hydrogen atom is: (RH = 1.097 × 10⁷ m⁻¹)
Lyman: n₁=1, third line n₂=4. ν̄ = RH (1 - 1/16) = 1.028×10⁷ m⁻¹.
Ref: NCERT Class 11 Chemistry > Chapter 2: Structure of Atom > Topic: Developments Leading to Bohr Model - Electromagnetic Radiation and Spectrum