Spectrum Wikipedia

Spectrum - Wikipedia.

A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum.The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism.As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum..

https://en.wikipedia.org/wiki/Spectrum.

Visible spectrum - Wikipedia.

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.A typical human eye will respond to wavelengths from about 380 to about 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 400-790 terahertz..

https://en.wikipedia.org/wiki/Visible_spectrum.