- Natural light (like sunlight or light from a bulb) is usually unpolarized, meaning its electric field vibrates in many different directions perpendicular to the direction of travel.
- When natural light interacts with certain surfaces or materials—such as reflecting off water, glass, or the atmosphere—the vibrations in some directions get absorbed or diminished more than others.
- For example, light reflected from a surface tends to be partially polarized because the reflected waves vibrate mostly in a plane parallel to the surface.
- Similarly, when sunlight scatters in the atmosphere (called Rayleigh scattering), the scattered light becomes partially polarized, especially at 90 degrees from the sun’s direction.
- Also, polarizing filters (like Polaroid sunglasses) work by blocking light waves vibrating in all but one direction, creating polarized light from originally unpolarized natural light.
So, polarization of natural light occurs mainly through reflection, scattering, or transmission through certain materials that filter out or reduce vibrations in certain directions, leaving light waves vibrating predominantly in one plane.