How polarising filters work. This animation shows the effect of polarisers on light. At the start of the animation, normal light is seen, with its constituent photons shown with their electric field component (white arrows) oscillating at random angles, perpendicular to the direction of propagation. The horizontal and vertical components are represented by red and green arrows respectively. During the animation, two linear polarisers are used. The first lets through only the photons with vertically-oriented electric fields. The second filter, perpendicular to the first one, blocks the remaining electric field oscillations, producing complete polarization and blocking the passage of light (referred to as 100 percent extinction). Polarised sunglasses work by having one of this type of filter, oriented to block light reflected from the ground and surfaces, hence reducing glare.