ABSTRACT
A hydrogen atom emission spectrum is obtained by passing an electric discharge through a tube of low-pressure hydrogen gas (to form excited hydrogen atoms) and dispersing the emitted light into its constituent wavelengths using a prism or diffraction grating. The resulting spectrum consists of light emitted at discrete frequencies only. The emitted frequencies, v, occur in distinct groups with a regular pattern in different regions of the electromagnetic spectrum (Fig. 1). The frequencies conform to a very simple expression:
The sequence is known as the Rydberg series and the quantity RH= 109 677 cm−1 is called the Rydberg constant. The emission with frequencies corresponding to n1=1 is called the Lyman series and occurs in the ultraviolet. The Balmer series (n1=2) occurs in the visible region. The Paschen, Brackett and Pfund series (n1=3,4,5, respectively) are in the infrared.
