Opacity refers to the degree to which an object, area or surface obscures objects or space beyond.

  • Different processes can lead to opacity including absorptionreflection, and scattering.
  • An entirely opaque substance transmits no light, and therefore reflects, scatters, or absorbs all of it.
  • When light strikes an interface between two media some light may be reflected, some absorbed, some scattered. The remainder undergoes refraction and is transmitted through the second medium.
  • So, opacity is the measure of impenetrability to electromagnetic radiation, especially visible light by a material.
  • An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through).
  • Both mirrors and carbon black are opaque.
  • Opacity depends on the wavelengths of the light being considered. For instance, some kinds of glass, while transparent in the visual range, are largely opaque to ultraviolet light.