• Reflectance
  • The ratio of reflected radiation to that of the incident radiation on a surface.
Abstract from DBPedia
    The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic structure of the material to the electromagnetic field of light, and is in general a function of the frequency, or wavelength, of the light, its polarization, and the angle of incidence. The dependence of reflectance on the wavelength is called a reflectance spectrum or spectral reflectance curve.

    ある面に入射する光束を、この面で反射する光束をとすると反射率Rは下の式で示される。 また、媒質の屈折率を、反射する面の屈折率をとすると、光がその面に対して垂直に入射するときの反射率Rは下の式で示される。