Spectrum of light

Indicates the range of wavelengths emitted by a given lamp. For light therapy lamps, the spectrum is usually given in nanometers (nm) and describes the part of the light spectrum in which the device operates. This is an important parameter because it affects how light affects vision, the biological clock, and the overall comfort of the user. Visible light to the human eye is approximately in the range of 380-780 nm. Shorter wavelengths (around 380-500 nm) correspond to the violet and blue parts of the spectrum, medium wavelengths (approx. 500-600 nm) to green and yellow, and longer wavelengths (approx. 600-780 nm) to orange and red. Light therapy lamps are usually designed to emit primarily visible white light, often with suppression or filtering of the UV component (UVA and UVB), which begins below approximately 380 nm and can be harmful to the skin and eyes. In light therapy, it is important that the light spectrum supports the natural regulation of the circadian rhythm. From this perspective, the proportion of shorter wavelengths in the blue range (approximately 450–490 nm) plays a particularly important role, as these strongly influence melatonin production and alertness. Manufacturers therefore often optimize the spectrum so that the lamp has an effective effect on the internal biological clock, while also being comfortable and safe for prolonged viewing. In the technical description, the light spectrum can be specified, for example, as a specific range (e.g., 420–750 nm) or as the dominant wavelength or spectrum composition in a graph. In common practice in e-shops, customers will most often only find information that the lamp uses visible white full-spectrum light or that it does not emit UV radiation. If a numerical range in nm is given, this helps experts and more demanding users to assess whether the light is suitable for a specific use (e.g., morning light therapy, autumn and winter depression, or sleep disorders).