{"id":484,"date":"2026-07-13T22:06:43","date_gmt":"2026-07-13T22:06:43","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=484"},"modified":"2026-07-13T23:30:12","modified_gmt":"2026-07-13T23:30:12","slug":"polarization-of-light","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/waves\/polarization-of-light\/","title":{"rendered":"What Is Polarization of Light?"},"content":{"rendered":"\n
Definition<\/div>

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Polarization of light is the orientation of a light wave’s electric-field oscillations relative to its direction of travel. Because light is a transverse electromagnetic wave, its vibrations can be filtered so they lie in a single plane, creating polarized light. Malus’s law, I = I0<\/sub>cos2<\/sup>\u03b8, gives the fraction of intensity a polarizer transmits.<\/p>\n<\/p><\/div>\n

Tilt a pair of polarized sunglasses in front of a phone screen and rotate them slowly. At one angle the screen looks perfectly normal; a quarter-turn later it goes almost completely black. Nothing about the phone changed \u2014 you simply rotated a filter across light that was already lined up in one direction.<\/p>\n

That hidden “direction” carried by light is what polarization is all about. It is why glare vanishes off a wet road, why 3D cinema glasses work, and why the very screen you are reading this on lights up at all.<\/p>\n

What Is Polarization of Light?<\/h2>\n

Polarization of light describes which way a light wave’s electric field points as the wave races forward. Light is an electromagnetic wave<\/a>, so it carries an electric field and a magnetic field that both oscillate at right angles to the direction of travel. Polarization is simply the label for the direction of that electric-field vibration.<\/p>\n

Picture flicking a rope tied to a post. Shake your hand up and down and the wave travels along the rope while the rope itself moves vertically \u2014 that is a vertically “polarized” wave. Shake side to side and you get a horizontal one. Now slide a fence with vertical gaps over the rope: the vertical wave slips through, the horizontal one is blocked. A polarizer does exactly this to light.<\/p>\n

In everyday polarization<\/a>, most light around you is unpolarized<\/strong>. Sunlight and a light bulb pour out countless tiny waves whose electric fields point in every direction at once. Only after light bounces, scatters, or passes through the right material does one direction win out \u2014 and the light becomes polarized.<\/p>\n

What Are the Types of Polarization?<\/h2>\n

Light has three polarization states \u2014 linear, circular, and elliptical \u2014 plus the everyday unpolarized case where the field points every which way. The type depends on how the electric-field vector behaves from one instant to the next.<\/p>\n

Linear (plane) polarization<\/h3>\n

The electric field stays locked to a single line \u2014 vertical, horizontal, or any fixed angle. This is the state produced by a Polaroid filter, and it is the case Malus’s law describes.<\/p>\n

Circular polarization<\/h3>\n

Here the field keeps a constant strength but its direction rotates steadily, tracing a corkscrew as the wave advances. It can spin clockwise or anticlockwise, and it is the trick behind modern 3D cinema glasses.<\/p>\n

Elliptical polarization<\/h3>\n

The most general case: the field both rotates and changes length, so its tip sweeps out an ellipse. Linear and circular polarization are really just the two neat extremes of this broader family.<\/p>\n

Unpolarized light<\/h3>\n

No single direction dominates. The field jitters through every orientation at random \u2014 this is natural light straight from the Sun or a filament before anything acts on it.<\/p>\n

These states are not just textbook labels \u2014 they fall straight out of Maxwell’s equations for a transverse wave. For a rigorous, university-level derivation of the linear, circular, and elliptical cases, see MIT’s OpenCourseWare treatment of polarization<\/a>.<\/p>\n

The Malus’s Law Formula<\/h2>\n

Malus’s law states that when linearly polarized light of intensity I0<\/sub> meets a polarizer whose axis sits at angle \u03b8 to the light’s polarization, the transmitted intensity is I0<\/sub> multiplied by the square of the cosine of that angle.<\/p>\n

I = I0<\/sub> cos2<\/sup>\u03b8<\/div>\n

Each symbol carries a clear meaning and unit:<\/p>\n