Line spectrum of hydrogen

   When the electron shell of a hydrogen atom is excited, it will oscillate in its natural frequency and so the electron present in the shell. This oscillation of the electron causes the emission of the shortest wavelength Lyman series photon and the electron jumps to an outer transitory shell (see how light is emitted). The jumping of the electron depends on the degree of the excitation of a shell. i.e., a low-level excitation of a shell causes, the electron in the shell to jump to a nearer outer transitory shell. But, a high-level excitation of the shell causes due to the high-amplitude oscillation of the shell, the electron jumps to a more outer transitory shell.
   When the electron shell of a hydrogen atom is excited in a discharge lamp by a low-energy electron, the hydrogen atom emits the shortest wavelength Lyman photon and the electron jumps to a near outer transitory shell. If there is no further excitation for the atom, the electron will instantaneously fall back to the electron shell. But, if the transitory shell, to which the electron has jumped, is simultaneously excited by some ways, the electron again emits a Lyman photon in a longer wavelength. This type of excitation of the transitory shell which is very close to the electron shell of a hydrogen atom is the reason for the "fine structure" (splitting of the spectral line).
   But, if the electron shell is excited by a high-energy electron, the electron emits the shortest wavelength Lyman photon, but the amplitude of the photon will be greater because of the high-amplitude oscillation of the electron shell. This oscillation causes the electron to jump to a "further outer" transitory shell. If there is no further excitation for the atom, the electron will instantaneously fall back to the electron shell. This fall back causes the electron shell to be excited in a nominal fashion and the emission of a low-amplitude photon in the shortest wavelength. 
   But if the transitory shell, to which the electron has jumped, is simultaneously excited by some ways the electron emits a Balmer series photon and jumps to a further outer transitory shell. In this way, for every jumping of the electron to a more and more outer transitory shells and the excitation of those transitory shells can cause the emission of more-longer wavelength like Paschen series, Brackett series, and Pfund series photons. These processes can be continued until the electron is expelled out of the atom and to turn the atom into plasma of hydrogen at very high temperature.

See Structure of atom