True white light is made up of all the colours in the visible colour spectrum.
An incandescent light bulb emits a near complete visible spectrum – “true white light”.
The phrases “true white light”, “natural light” and “visible colour spectrum” are common place in our society, but what do they define? Most people are aware that true white light can be split in a prism by way of a process called refraction to show all the colours of the rainbow. In fact a rainbow is merely another example of this phenomenon: the white light from the sun is refracted in water particles in the atmosphere to show the colour spectrum of the sun light, which we know as a rainbow.
An incandescent bulb can be compared to the sun, as it emits almost every frequency of light. Similarly to the sun, the white light of a bulb can be refracted to see a continuum of different colours. This feature of a bulb is essential for some applications which require a complete spectrum of all colours.
“White” light can however also be approximated by mixing three different coloured lights together. The RGB connectors on some Televisions or projectors refer to the three colour constituents red, green and blue. If you look at a TV screen with a magnifying glass, you will see that it is made up of very small illuminator squares. These squares are each collated in groups of red, green and blue illuminators. The colour your eye will detect whilst watching TV depends on which of these illuminators is excited and to what extent. For example, if only the red and green illuminators are excited, the screen point will appear yellow. If the blue illuminator is then added, the screen point will appear white.
“White” light is also emitted for instance by fluorescent tubes or so called white LED’s which work on the principal of excited phosphors. Once again, this light consists of only some wavelengths of light which is why many people refer to them as “unnatural” light sources.
