According to the principle of light generation, electric light sources are mainly divided into two categories.

A. One type of electric light source is based on thermal radiation as the principle of light radiation, including incandescent lamps and tungsten halogen lamps. They all use tungsten filaments as radiators. After being energized, they can reach incandescent temperature and generate thermal radiation. This kind of light source is collectively referred to as thermal radiation light source, and it is still an important lighting source at present, with a large number of production.

B. Another type is various gas discharge light sources, which mainly produce light radiation in the form of atomic radiation. According to the pressure of the gas in these light sources, they can be divided into low-pressure gas discharge light sources and high-pressure discharge light sources.