A bright-line spectrum is produced whenever atoms in a gaseous state are excited by an electric discharge to emit radiation. The spectrum consists of a series of narrow bright-lines of characteristic color separated by regions of darkness. The number of the lines, their color, and their relative positions to each other are characteristic of the element. Each bright line represents light of a particular wavelength or frequency. Band spectra are produced by excited molecules, although high resolution spectroscopy now shows that they are in fact very many bright lines very close together.
Spectroscopy is the observation and interpretation of spectra.
In this experiment, we shall study the spectral lines of the simplest element, atomic hydrogen. Since the discovery of the visible bright-line spectral lines for hydrogen, other bright lines have also been discovered with wavelengths smaller and larger than those of visible light. Several other series of lines, each named after their discoverers, have been found. Bohr further assumed that whenever an electron changed from one energy level to another, it did so instantaneously emitting or absorbing energy depending on the difference between the energy levels of the two states. The accepted value for Rydberg's constant is 10973732 m -1 .