The reflectance of the surface of a material is its effectiveness in reflecting radiant energy.

  • Reflectance is the fraction of incident electromagnetic power that is reflected at the boundary. Power = energy x time.
  • Reflectance is a component of the response of a material to the electromagnetic properties of light, so a function of its:
  • Given that reflectance is a directional property, most surfaces can be divided into those that give specular reflection and those that give diffuse reflection.
  • For specular surfaces, such as glass or polished metal, reflectance is nearly zero at all angles except at the angle visible to an observer.
  • For diffuse surfaces, such as matte white paint, reflectance is uniform in all directions so radiation is reflected at all angles equally or near-equally.
  • Most practical objects exhibit a combination of diffuse and specular reflective properties.