Definition | Black light – Wood light

The wavelengths of the light so-called "black light" (or Wood light) begin at the end of the spectrum visible – purple side, around 405 nanometers – and extend to theultraviolet – around 375 nanometers.

Black light can be produced:

• through fluorescence in the case of low pressure tubes;
• or by the arc at mercury in high lamps pressure.

Uses of black light: medicine, detection of counterfeit banknotes…

Black light is used in various fields.

In medicine, it allows, for example, to observe the skin in depth and thus to diagnose lesions invisible to theeye naked such as yeast infections or problems with pigmentation.

Black light having the characteristic of highlighting synthetic fibers, it makes it possible to spot false banknotes: real ones do not contain them. Be careful however, because the euro banknotes have invisible ink prints that reveal themselves in black light.

Black light also highlights certain fluorescent bodies. So it is often used to create effects in the evenings.

Black light and health: what dangers?

Inherently, black light can have health impacts and more particularly on the skin (photosensitization) or on the eyes (conjunctivitis). In practice, the National Research and Security Institute for prevention of accidents of work and occupational diseases ensures that, when the exposure takes place more than 1.5 meters away, the risks disappear.