Light, Color, and Polarization

The physics of color begins with light, which is a form of electromagnetic radiation. Visible light spans a band of wavelengths that the eye perceives as the colors from red through to violet. Objects gain their color through the way they interact with light. Light emission occurs when a material gives off light, while absorption occurs when a material takes in particular wavelengths and reflects or transmits the rest. A red filter, for example, transmits red light and absorbs much of the green and blue, which is why colored filters change the appearance of what is seen through them.

Color mixing depends on whether light or pigment is being combined. Adding light follows the additive system: red, green, and blue light combined together produce white, and pairs of these produce other colors. Mixing pigments or inks follows the subtractive system, because each pigment absorbs some wavelengths and reflects others; combining pigments removes more light and darkens the result. This distinction explains why mixing colored lights and mixing paints give different outcomes, and it underlies practical processes such as color printing.

Polarization is a further property of light related to the orientation of its waves. Light waves can vibrate in many directions, and a polarizing filter passes only those vibrating in a particular plane. Two such filters crossed at right angles block most of the light, a striking effect often shown in demonstrations. Interactive animations and applets can illustrate these behaviors — emission and absorption, the mixing of light and pigments, and polarization — by letting the effects be adjusted and observed dynamically.

Frequently asked questions

What is the difference between color addition and color subtraction?

Color addition combines beams of light, with red, green, and blue producing white. Color subtraction combines pigments that absorb light, so mixing them darkens the result.

How does a colored filter work?

A colored filter transmits light of its own color and absorbs much of the rest, so a red filter passes red light while removing most green and blue.

What does polarization of light mean?

Light waves can vibrate in different directions, and polarization refers to restricting that vibration to a single plane, as a polarizing filter does.