This section is part of the HSC Physic syllabus Module 7: Nature of Light under Electromagnetic Spectrum.
Light gets a lot more interesting when we pass it through a discharge tube, which is explained below. This is an example of an investigation to examine a variety of spectra produced by discharge tubes, reflected sunlight or incandescent filaments.
When elements are energised, their carriers can get excited and jump between valency levels. This change in state causes a release of energy which can be seen as different forms of light.
The discharge tube is a tube containing charged electrodes and filled with a gas in which ionization is induced by an electric field.