How is a bright line spectrum produced?

A bright-line spectrum is produced when gases under low pressure are thermally or electrically induced to discharge different wavelengths of bright lines on a dark background. A bright-line spectrum is also known as an emission spectrum.

The process of separating visible light into its individual spectral lines is called dispersion, where each line corresponds to a wavelength or frequency that matches a specific color. The three types of spectra that can be produced via dispersion include continuous, bright-line or dark-line. A continuous spectrum contains all frequencies of visible light. A bright-line spectrum generates spectral lines instead of a continuous spectrum, whereas a dark-line spectrum, also known as an absorption spectrum, is superimposed by a continuous spectrum. Bright-line and dark-line spectra are typically used in identifying chemical elements.