Hydrogen Emission and Absorption Spectrum

The Hydrogen Emission Spectrum consists of a series of coloured lines resulting from the transition of its electron from one energy level down to another; a photon being emitted with its energy equal to the difference between the energy levels.

There are many clusters of lines in the Hydrogen spectrum. Only one is in the visible region: the Balmer series,  named after the man who worked out the mathematical formula for it. As a result of his mathematical analysis of the wavelengths of the visible hydrogen lines; he predicted many more which were later found by experiment in the ultraviolet region. Rydberg generalised Balmer's formula and then predicted other series of spectral lines which were subsequently observed by experiments: (the Lyman series) in the ultraviolet, and in the infrared region ( the Paschen series and the Brackett Series) and well as others in the far infrared etc.

The Energy Levels of the Hydrogen Atom:

The Transitions between Energy Levels of the Electron either results from absorption of a photon of the required energy or emission of a photon of that same energy. The chart below shows many of the possible emissions due to electrons falling from one excited state to a lower energy state.

The absorption spectrum for Hydrogen, arises when we view white light coming through hydrogen gas, as is typically observed by astronomers when they analyse the light coming from distant stars; the light from those stars passing through clouds of cold hydrogen gas.  The hydrogen atoms in the clouds absorb light of the frequency matching the difference in energy levels of the hydrogen atom, raising an electron up a level or number of levels. This depletes the light coming from the star for these particular wavelengths, thus creating dark lines in a continuous spectrum.