Polarising filter, animation. A polarising filter (blue) allows light or other electromagnetic radiation whose electrical component lies at right angles (bottom) to the filter to pass through, but blocks those that are parallel (top) to the filter. As the top wave enters the filter it causes electrons to move (bright light in the column). These electrons absorb energy from the wave and absorb (filter) it. The electrons are constrained in the column and cannot move horizontally and so cannot absorb the energy from the bottom wave. Filters are used in sunglasses and photography to reduce glare.