Line spectrum of hydrogen atom: How a hydrogen atom emits its line spectrum

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 (because, that frequency is the natural frequency of the electron shell of hydrogen atom) and jumps from the shell to an outer transitory shell. If there is no any further excitation for the atom, the electron will instantaneously fall back to its original shell. Also, this fall into the shell can cause, the shell get excited in a nominal fashion and the emission of a low intensity photon in the natural frequency of the shell (additionally, this oscillation of the electron can cause, it to jump to a nearer outer transitory shell. If an energetic electron from an external source simultaneously excites this transitory shell, the electron will emit a Lyman series photon in a longer wavelength). But, if the transitory shell (to which the electron has initially jumped) is simultaneously excited by some ways (for example, collision of an energetic electron from an external source --in a discharge tube-or collision between atoms), the electron will again get excited and emit a photon in a longer wavelength, in the natural frequency of that transitory shell. Also, this excitation of the electron causes a further jumping to a more outer transitory shell, and these processes can be continued until the electron is expelled out from the atom and to turn the atom into plasma of hydrogen at a very high temperature. For every jumping of the electron to a more and more outer transitory shells, and the excitations of that transitory shells can cause the emission of more and more long wavelength photons, and this is the reason for the emission of more long wavelength photons like Balmer series, Paschen series, Brackett series, Pfund series etc. http://www.physics-edu.org/