What does visible light mean?

Light or "visible light" refers to the visible region of the electromagnetic spectrum – that is, the range of wavelengths that trigger brightness and colour perception in humans. It lies between UV and infrared radiation.

Light and the eye

The wavelengths of light penetrate as far as the retina in the eye and the dermis in the skin. Most people can perceive wavelengths of between about 400 nanometres (nm) and 780 nm visually. Rather than being clear cut, the boundaries of the visible region of the spectrum for humans exhibit fluid transitions. Moreover, a person's eyesight and sensitivity to light vary over their lifetime due to ageing processes in the eye. Especially for the short-wavelength section of the visible spectrum (blue light), the transparency of the lens decreases with age.

The principal natural radiation source for light is the sun, but our everyday lives also feature a multitude of artificial light sources.

*This table is for indicative purposes only. The transitions between the colours are fluid.

The significance of light

Light is not only responsible for allowing us to see our surroundings but also has other biological effects and influences the sleep/wake cycle, among other things. Light has long been used for medical and cosmetic purposes. Many lasers and IPL devices ("flash lamps") operate with different wavelengths of light. For example, light with a relatively high proportion of blue light is used in light therapy devices or daylight lamps to treat "winter depression" or to set the "body clock" when everyday life involves little natural light.

There is a risk of damage, especially to the eyes and possibly also to the skin, if the intensity of light exceeds certain effect thresholds.