Dimming behaviour of incandescent lamps. Relative luminous flux F and colour temperature in dependence on the relative voltage U/Un. Voltage reduction causes an over-proportional drop in luminous flux.
The general service lamp is a thermal radiator. Electrical current causes a metal filament to glow. Part of the radiated energy is visible as light. When
dimming, the reducing temperature causes the light spectrum to shift towards the range of longer wavelengths - the warm white light of the incandescent lamp changes to the red heat of the filament. The maximum radiation is in the infrared range. A lot of thermal radiation is generated in comparison to the visible component; conversely there is very little UV radiation. The continuous
spectrum of the incandescent lamp results in an excellent
colour rendition.
