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.