ABSTRACT
Everyone capable of sight is a practitioner of reflectance spectroscopy in the visible
region of the spectrum. We are constantly bathed by light, some which is character-
ized by wavelengths between 400 nm (i.e., blue light) and 650 nm (i.e., red light).
When our eyes perceive, for instance, a red piece of clothing, we are actually observ-
ing the reflected portion of the irradiation light. The clothing absorbs the blue light,
reflects the unabsorbed red light, our eyes perceive the reflected red light, and our
mind then interprets this measurement to conclude that the piece of clothing was
actually red. However, our perception can be altered by changing the conditions
of the experiment. If the same piece of clothing is now irradiated only with blue
light, that light will be completely absorbed, and no light will be reflected.
Because in that case our eye would not be able to detect any reflected color from
the clothing, we would then conclude that the same piece of clothing was black.