TABLE OF CONTENTS The spectral composition of the light emitted from a light source undergoes various changes in the process of scattering, reflection, refraction, transmission, and absorption. As a consequence, objects under one illumination send light of different spectral compositions to our visual system and they produce our perception of various colors. There are many ways materials or light sources can modify or generate light of different spectral compositions (see, e.g., [276, 391, 693, 1038], for more details).
According to Nassau [693], color can be produced by: (1) incandescence (light emitted by heated bodies), (2) gas excitation, (3) atomic or molecular vibration and rotation, (4) transition metals in a ligand field, (5) orbital transitions in organic molecules, (6) charge transfer, (7) energy bands and impurities in metals and semiconductors, (8) color centers, (9) dispersive refraction and polarization, (10) scattering, (11) nonlinear optical effects, (12) interference, (13) diffraction, etc. It is clear that causes of color are many. However, it should be noted that this classification of different causes is a matter of convenience and different causes should not be taken as mutually exclusive. After all, light matter interaction can be described on a very fundamental level by a single theory called quantum electrodynamics. The following sections discuss some of the common causes of color.
The majority of surface colors are due to the selective absorption by the pigments embedded in the surface material. Although photons of visible light (1.7 3.1 eV) have energy on the low side for...
