The fluorescent lamp is a low-pressure discharge lamp that works using mercury. The gas filling consists of an inert gas that makes the ignition easier and controls the discharge. The mercury vapour emits ultraviolet radiation upon excitation. Fluorescent substances on the inside surface of the discharge tube convert the ultraviolet radiation into visible light using fluorescence. A voltage surge is used to ignite the lamp. The discontinuous spectrum of fluorescent lamps has a poorer colour rendition property than that of incandescent lamps with a continuous spectrum. The colour rendition of fluorescent lamps can be improved at the cost of luminous efficacy. Conversely, increasing the luminous efficacy causes a worsening of the colour rendition. The light colour can be in the warm white, neutral white or daylight white range, depending on the proportion of the individual fluorescent substances.