Page 5 - Understanding light, colour and hair colour

All wavelengths are registered on a spectrum called the Electromagnetic
Spectrum.(Please see Fig. 3)

You will notice from this linear version of the electromagnetic spectrum,

it actually contains a visible spectrum and an invisible spectrum.

The visible spectrum contains wavelengths from 400nm to 700nm. The

invisible spectrum contains infra red and radio wavelengths between

700nm to 1metre or greater at the low end of the electromagnetic
Spectrum, with ultra violet rays, x-rays and gamma rays from 400nm to

100th of a nanometer at the high end of the electromagnetic spectrum.