When solar radiation hits a target surface, it may be transmitted, absorbed or reflected.
Different materials reflect and absorb differently at different wavelengths. The reflectance
spectrum of a material is a plot of the fraction of radiation reflected as a function of the incident
wavelength and serves as a unique signature for the material. In principle, a material can be
identified from its spectral reflectance signature if the sensing system has sufficient spectral
resolution to distinguish its spectrum from those of other materials. This premise provides the
basis for multispectral remote sensing