What are Brewsters Fringes and why do I need to know about them?
Brewster’s Fringes occur when 2 panels of high quality glass are placed in parallel (for example when a sacrificail layer of glass is placed onto glass flooring) and can create an “oily” illusion. This can often be mistaken for liquid caught between the 2 panels of glass, however in reality are just an example of the way light behaves. Brewster’s Fringes are wavelengths of light meeting up with each other when they are exactly 180 degrees out of phase – an example of this phenomenon is known to physicists as the ‘interference’ of light. Brewster’s Fringes only occur when the surfaces of the glass are flat and the two panes of glass are parallel to each other. What happens is that some of the incident light from the Sun meets light reflected from one of the surfaces of the insulating glass in such a way that they are 180 degrees out of phase and cancel each other out, thereby giving rise to a fringe (sort of oily looking) effect, small in area on the glass when viewed from a particular
