Important Materials Theory - Photographic Rendering with V-Ray for SketchUp - page 237

Note
In the case of frequency, the colors are reversed as red has the lowest frequency
while violet has the highest. In fact, the terms infrared and ultraviolet are based
on the frequency and not wavelength values of the visible spectrum. Infra being
a Latin word that carries the thought of something below , while ultra, also of Latin
origin, means beyond or on the far side of .
In Chapter 5 , Understanding the Principles of Light Behavior, we also highlighted
how in the 1800s, physicist Lord William Kelvin produced what is now known as the
Kelvin color temperature scale. This was based on his observations of how a black
body emitter (a block of carbon) when heated, produced a range of colors that fol-
lowed a definite, measurable progression.
The scale assigns a numeric value in degrees Kelvin to each step of the progression,
ranging from black through red, onto orange and then up to white, and beyond
that into the blue part of the spectrum. In other words, the carbon emitted varying
wavelengths of light according to the amount of heat it was generating.