Opacity refers to the extent to which an object or surface prevents light from passing through, thereby obstructing light from reaching objects or space beyond.
- Opacity is influenced by factors such as absorption, reflection, and scattering of light. An entirely opaque substance reflects and absorbs all incident light, allowing no transmission or scattering.
- When light strikes the boundary between two media, some of it is reflected, some is absorbed, and some is scattered. The remaining light is refracted and transmitted through the second medium. Opacity measures how effectively this second medium obstructs the passage of light.
- An opaque object is neither transparent (which allows all light to pass through) nor translucent (which permits partial light transmission).
- The opacity of certain materials can vary with the wavelength of light. For instance, some types of glass are transparent to visible light but opaque to ultraviolet radiation.