Whiteness Index meaning:
Whiteness is a parameter of an ideal reflecting surface area that neither absorbs nor transmits light. On the contrary, it reflects light at equal intensities in all directions. In 1981, CIE recommended a formula which is known as “CIE Whiteness.” These indices are specified by the CIE under the illuminant D65 and illuminant C combined with standard observer (either 2° or 10° observer). The performance of the bleaching effect is also determined by reflectance. This reflectance can be measured by a “Spectrophotometer” or “Reflectometer”. Here, reflectance value 100 means a perfect white whereas 0 means perfect black.
Whiteness is defined as a measure of how closely a surface matches the properties of a perfect reflecting diffuser, i.e. an ideal reflecting surface that neither absorbs nor transmits light, but reflects it at equal intensities in all directions. For the purposes of this standard, the color of such a surface is known as preferred white.