Chapter 27 Color

Selective Reflection  Atoms absorb light at or near their natural frequencies.  Atoms reradiate light at other frequencies Leaves must absorb everything that is not green Petals must absorb everything not red.

Different Illumination  What color are the petals of the rose under blue light?  Black  What color are the leaves under green light?  Green

What is absorbed?

Selective Transmission  Color of a transparent object is the color of the light it transmits.  Blue glass appears blue because it absorbs all other colors.

Radiation Curve of the Sun

Simplified Radiation Curve Wavelength Real spectral colors Simplified

Color Addition CYANYELLOW MAGENTA These mixtures are the subtractive primary colors

Memorize these! Yellow Magenta Cyan White Play mixing the colors yourself

Traditional Color Wheel Colors equally spaced are said to be primary : Red-Yellow-Blue (RYB) or sometimes Violet-Orange-Green (VOG). neither RYB nor VOG is equidistant on a perceptually uniform color wheel RYB cannot mix all colors and we will not consider it further

Complimentary Colors G + R B + G B + R

Color Subtraction White Light XX Yellow Filter XX Blue Filter Black

Color Subtraction Green Dress Yellow Dress XX Cyan Light

Color Subtraction Yellow Dress XX Magenta Light Red Dress