Diffusion

In optics, diffusion results from any material that scatters light during transmission or reflection producing softened effects without sharp detail.

  • Objects produce diffuse reflections when light bounces off their surfaces and scatters in all directions.
  • Transparent and translucent materials transmit diffuse light unless their surfaces are perfectly flat and their interiors is free of any foreign material.
  • All objects obey the law of reflection on a microscopic level, but if the irregularities on the surface of an object are larger than the wavelength of light, the light undergoes diffusion.
  • A reflection that is free of the effects of diffusion is called a specular reflection.
  • Diffuse reflection takes place when light reflects off a rough surface. In this case, scattering takes place and waves are reflected randomly in many different directions and so no image is produced.

https://en.wikipedia.org/wiki/Diffuser_(optics)