Chapter 27 Color Selective Reflection v Atoms absorb

Chapter 27 Color

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

Different Illumination v What color are the petals of the rose under blue light? ØBlack v What color are the leaves under green light? ØGreen

What is absorbed?

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

Radiation Curve of the Sun

Simplified Radiation Curve Real spectral colors Simplified Wavelength

Color Addition CYAN MAGENTA YELLOW These mixtures are the subtractive primary colors

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

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 B+G G+R B+R

Color Subtraction White Light XX Yellow Filter XX XX Black Blue Filter

Color Subtraction Cyan Light XX Green Dress Yellow Dress

Color Subtraction Magenta Light XX Red Dress Yellow Dress