Polarization
. Polarization refers to the direction of the electric field in an electromagnetic wave. A wave whose electric field is oscillating in the vertical direction is said to be polarized in the vertical direction. The photons of such a wave would interact with matter differently than the photons of a wave polarized in the horizontal direction. The electric field in light waves from the Sun vibrates in all directions, so direct sunlight is called unpolarized. Sunlight reflected from a surface is partially polarized parallel to the surface. Polaroid sunglasses block light that is horizontally polarized and therefore reduce glare from sunlight reflecting off horizontal surfaces.