Why is the spectrum of tungsten filament incandescent?
Dense material, including high-pressure gas and plasma, according to the black body radiation issued a continuous spectrum.
With a continuous spectrum of light through the low-pressure gas, the corresponding position appears discrete black line.
The low pressure gas emits a discrete spectral line, and the brightness increases with increasing gas temperature.
Incandescent lamp is an ordinary light bulb, tungsten wire heating light, according to the black body radiation issued continuous spectrum, so from red to purple one continuous.
