CP Physics Mr. Miller

General Information  Sir Isaac Newton – first to realize white light composed of different colors  Prisms – separate white light into colors of light making up the visible light spectrum  Each color has its own wavelength and frequency  Higher frequency = greater energy  Red light – lowest frequency so least energy  Violet light – highest frequency so most energy

Seeing Colors  Color is the property of light reaching the eye  Objects absorb some colors and reflect others  We see the reflected colors!!

Color Rule #1  The color of an opaque object depends on the frequency of light it reflects.  All colors reflected and none absorbed = white  No colors reflected and all absorbed = black

Color Rule #2  Color of an opaque object depends on the color of light shown on it.  Red object - reflects red light  Shine white light on it – looks red  Shine red light on it – looks red  Shine green light on it – look black

Color Rule #3  Color of a transparent object depend on the color of light it transmits.  Blue filter transmits only blue light through it.  Shine white light on it – blue passes through.  Shine blue light on it – blue passes through.  Shine red light on it – no light passes through.

Visible Spectrum  ROY G BIV – red, orange, yellow, green, blue, indigo, violet  Polychromatic = many frequencies of light colors together  Monochromatic = single frequency of light

Primary Colors of Light  Red, Blue, Green  When added together they produce white light

Secondary colors of light  Magenta, Cyan, Yellow  Produced when two primary colors added:  Red + Blue = Magenta  Blue + Green = Cyan  Green + Red = Yellow

Complementary Light Colors  A primary light color and a secondary light color that will produce white light when added together  Complements:  Red + Cyan  Green + Magenta  Blue + Yellow

Primary Pigments  Pigments = chemicals which absorb certain frequencies of light and reflect others  Primary pigments absorb one primary color of light and reflect two primary colors  Magenta – absorbs green, reflects red and blue  Cyan – absorbs red, reflects green and blue  Yellow – absorbs blue, reflects red and green  So a primary pigment absorbs its complement!

Secondary Pigments  Absorb two primary pigments and reflect one primary pigment  Red, Blue, Green

Light colors vs. Pigments  Primary colors of light = secondary pigments  Secondary colors of light = primary pigments  Mixing colors of light = ADDITIVE process  More colors added – color of light gets lighter  Mixing pigments = SUBTRACTIVE process  Pigments absorb color, so more pigments absorb more colors of light and less reflected for us to see, gets darker