জৈব পিগমেন্ট বলতে কি যে কোনো জৈব পদার্থের পিগমেন্টকে বোঝায় ?
Pigments appear colored because they selectively reflect and absorb certain wavelengths of visible light. White light is a roughly equal mixture of the entire spectrum of visible light with a wavelength in a range from about 375 or 400 nanometers to about 760 or 780 nm. When this light encounters a pigment, parts of the spectrum are absorbed by the pigment. Organic pigments such as diazo or phthalocyanine compounds feature conjugated systems of double bonds. Some inorganic pigments, such as vermilion (mercury sulfide) or cadmium yellow (cadmium sulfide), absorb light by transferring an electron from the negative ion (S<sup>2−</sup>) to the positive ion (Hg<sup>2+</sup> or Cd<sup>2+</sup>). The other wavelengths or parts of the spectrum are reflected or scattered. The new reflected light spectrum creates the appearance of a color. Pigments, unlike fluorescent or phosphorescent substances, can only subtract wavelengths from the source light, never add new ones.
no