Mercury is used as a standard element in most cases. Knowing the wavelength, corresponding to different spectral lines, elements can be judged. Hartmann's method is employed to determine the unknown wavelength.

If a transparent substance is placed between a continuous source and a spectrometer, the substance absorbs a certain part of the spectrum. Hence in the continuous spectrum of the source, a few dark lines or bands appear. This spectrum is called absorption spectrum of the substance. This method is useful for manufacturing as well as for academic experiments. Constant Deviation Spectrometer (Model No: HO-ED-S-0203) can be used for the study of spectral series viz. emission spectra of elements, absorption spectra of compounds, quantitative spectrum analysis etc.

When a substance is heated, electrons first absorb energy, go to a higher energy level and eventually fall to a lower level, by emitting photons. Every element emits a characteristic spectrum of its own. There are certain important and prominent spectral lines associated with each element. These lines are used to distinguish one element from another. In the experiment to determine an element, spectrum of standard known source is pictured first.