The equation that scientists could use to find the wavelength of the emission lines of the hydrogen atom would be that of Balmer.
The wavelength of the emission lines of the hydrogen atom can be derived using the Balmer series:
1/λ
Where λ = wavelength, = Rydberg constant, and n = level of the original orbital.
The equation becomes applicable in getting the wavelength of emitted light when electrons in hydrogen atoms transition from higher (n) orbital to lower orbital (2) levels.