In layman’s terms, according to Google’s dictionary,
‘The natural agent that stimulates sight and makes things visible.’
Synonyms that may aid the understanding of light;
‘Illumination, brightness, luminescence, shining, radiance, glowing, glare’.
Light is generally, in layman’s terms, electromagnetic radiation that the eye can see, some light a person cannot see like IR (infrared) and UV (ultraviolet). Electromagnetic radiation makes up the weakest types like radio waves (wavelength in meters), infrared, visible light, ultaviolet light, x-rays and gamma rays (very energetic, short wave). The electromagnetic radiation is harmless at low wavelengths but can become very dangerous at short wavelengths like gamma rays that destroy and split DNA.
Light is made up of photons and is NOT ionizing and therefore visible light is referred to as ‘illumination’ as it is the observable property and effect of light NOT such as UV-C for example. A UV-C light source may glow with visible light as a byproduct, but the actual UV-C cannot be seen as it is not in the visible spectrum of light. Visible light is broken down into different wavelenghts, that make up a rainbow after a thunderstorm or the vivid colours that a prism splits light into, namely red, orange, yellow, green, blue and purple, all of these colours have a different wavelength and white light is a mixture of all of these wavelengths.
There has been a new trend with LED light sources taking over the market and a light meter stays a light meter unless a spectrometer is applied to measure the actual wavelengths emitted by a light source. Spectrometer type light meters are very expensive in comparison to affordable or normal light meters (and can sometimes be more complicated to use).
LED light sources are not standardized and a so-called ‘LED light meter’ stays ‘a light meter’ as every such light meter is calibrated acoording to a tungsten filament lamp, referred to as ‘Standard Illuminant A’ by the CIE, an international organization that defines HOW light should be correctly measured. An ‘LED light meter’ is marketing technique for low cost and value instruments and performs the same operations as a ‘light meter’. If the end user wants to measure LED light sources with a traditional light meter, applying a correction factor of around 1.2 is recommended, i.e. multiply your reading by 1.2 and in real terms is very little difference if any. Goldilux light meters do the job.
Tungsten as an element can be standardized in terms of its purity and produces a standard colour temperature of 2856 Kelvin. Various manufacturers have different manufacturing techniques and ingredients and produce differing LED light sources – also there is no defined standard that defines an LED diode according to colour temperature or colour rendering index. Different manufacturers add various amounts of Phosphor that affect the brightness of their LED diodes.
On the other hand, radiation (in the UV spectrum and beyond) is sterilizing and can sterilize water or foods that are irradiated for a longer shelf life in the supermarket or where perishable foods are sold. That is casually where UVGI (UV-C) comes in and Goldilux has UV-C probes and readout units to cater for that need.