Recall the frequency (ν) indicates the number of waves passing a given point per second and is expresses as cycles per second. Wavenumber (⊽) on the other hand stands for the number of waves connected in unit length that is per centimeter (cm⁻¹) or per meter (m⁻¹). Thus wavenumber is cm⁻¹.

Transition to the n = 2 level from n = 3, n = 4, n = 5, etc exited states constitute the Balmer series in the visible spectral region. The wavelength of these spectral lines can be calculated by the following equation.

⊽ = 1/λ = R[(1/n₁²) - (1/n₂²)]

n₁ = 2 and n₂ = 3, 4, 5, ...