Polarisation

Watch the town through a peephole with polarising foil. By tilting the peephole you can darken or lighten the windows, some windowsills will even start to play in otherwise invisible colours. The switching on and off of the individual windows in the buildings is due to two polarising foils. One is directly in the window and we look through the other in the peephole. From all the light waves the polarising foil lets pass only the part that has the right plane of electric field. Light is nothing other than an electromagnetic wave. The electric field of normal light chaotically changes into many directions but when we use polarised light its electric field is nicely streamlined. In other words, a foil made of a material with long chains of molecules works like a prison window grid and light like a long rod ??“ only correctly tilted light will pass through the molecule grid.