132. Explain in brief hydrogen spectra.

Hydrogen spectrum is an important example of line spectrum. The spectrum of hydrogen can be obtained by passing an electric discharge through the hydrogen gas taken in the discharge tube under low pressure. The radiation thus obtained is analysed with the help of a spectroscope The spectrum thus obtained contains a large number of lines present in the ultraviolet, visible and infra-red regions. These lines have been grouped into five series, each named after the name of the discoverer.
These are:
(i) Lyman series..........Ultraviolet region
(ii) Balmer series..........Visible region
(iii) Paschen series
(iv) Brackett series.........Infrared series

Though hydrogen atom contains only one electron but so many lines are obtained in the spectrum.


It is because of different possibilities of its excitation in its different energy levels. The lines in the visible region can be directly seen on the photographic film while the position of lines in the ultraviolet and infrared regions are located employing different techniques.