Electric light sources that we identify as white are used in most of today's general lighting applications. These light sources are not white in the sense of containing equal amounts of all colors in the visible spectrum, as in the diagram of the electromagnetic spectrum. Each is deficient in some portion of the spectrum, which affects the appearance of colors and the apparent warmness or coolness of the environment. Isaac Newton found that a narrow beam of sunlight passing through a glass prism would disperse to show all the colors in the visible spectrum. This effect was known, but it was thought that the glass somehow filtered or tinted the light.
Some scientists believe the shift to be a temporary condition of adaptation.
For example, when we move back and forth between an exterior with full spectrum natural light and an interior with a color deficient source, we perceive the colors to be the same under both conditions. On the other hand, an article purchased under one light source may look altogether different when viewed at home under another source. Light is technically a form of electromagnetic energy. The electromagnetic spectrum contains many different wavelengtbs that are identified in categories of frequencies, such as gamma rays, X rays, ultraviolet rays, and so forth. The human eye is sensitive to only a small part of the total identified as visible light.