White is a color, the perception which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in near equal amount and with high brightness compared to the surroundings.

Since the impression of white is obtained by three summations of light intensity across the visible spectrum, the number of combinations of light wavelengths that produce the sensation of white is practically infinite. There are a number of different white light sources such as the midday Sun, incandescent lamps, fluorescent lamps and white LEDs. The impression of white light can also be created by mixing appropriate intensities of the primary colors of light — red, green and blue (RGB) — a process called additive mixing, as seen in many display technologies.

White light reflected off objects can be seen when no part of the light spectrum is reflected significantly more than others and the reflecting material has a degree of diffusion. This is seen when transparent fibers, particles, or droplets are in a transparent matrix of a substantially different refractive index. Examples include classic "white" substances such as sugar, foam, pure sand or snow, cotton, clouds, and milk. Crystal boundaries and imperfections can also make otherwise transparent materials white, as in the milky quartz or the microcrystalline structure of a seashell. This is also true for artificial paints and pigments, where white results when finely divided transparent material of a high refractive index is suspended in a contrasting binder. Typically paints contain calcium carbonate and/or synthetic rutile with no other pigments if a white color is desired.

Etymology

The word white comes from the Common Germanic hwitaz though the Old English word hwīt.

Paint

In painting, white can be crafted by reflecting ambient light from a white pigment, although the ambient light must be white light, or else the white pigment will appear the color of the light. White when mixed with black produces gray.Fact: date=May 2008 To art students, the use of white can present particular problems, and there is at least one training course specializing in the use of white in art.Fact: date=May 2008 In watercolor painting, white areas are the absence of paint on the paper.

Light

In the science of lighting, there is a continuum of colors of light that can be called "white". One set of colors that deserves this description is the color emitted via the process called incandescence, by a black body at various relatively-high temperatures. For example, the color of a black body at a temperature of 2848 kelvins matches that produced by domestic incandescent light bulbs. It is said that "the color temperature of such a light bulb is 2848 K". The white light used in theatre illumination has a color temperature of about 3200 K. Daylight can vary from a cool red up to a bluish 25,000 K. Not all black body radiation can be considered white light: the background radiation of the universe, to name an extreme example, is only a few kelvins and is quite invisible.