a Flickr photoset contains images of light patterns made by glass and transparent objects…
The refraction pattern of white light through an opalescent blue/white glass sweatmeat dish with the “Vesta Venetian” pattern.
Opalescence in glass is caused by small particles,crystals or phase separation which scatter light to give a particular colour effect. This colour is determined by the number and size of the particles and the spacing between them. The same is true for other light scattering phenomena e.g. the sky is blue because of light scattering from the nitrogen molecules, sunsets are red/yellow from the scattering by dust particles in the atmosphere, cigarette smoke is blue because of the scattering from the small soot particles etc etc.
When looked at in reflected light opalescence or milk glass shows a pale blue/white colour (like Lalique glass or Sabino glass of the early 1900′s) but in transmitted light, as shown in this shot, when a light is shone through, golden yellow colours can be seen. The regular refraction patterns are caused by the surface patterns of the moulded “Ventian” pattern of this particular glass dish.