19-Oct-15 Physics 1 (Garcia) SJSU Chapter 27 Color

19-Oct-15 Physics 1 (Garcia) SJSU Spectrum of Visible Light

19-Oct-15 Physics 1 (Garcia) SJSU Wavelengths & Photons Red Photon Blue Photon Green Photon Yellow Photon Prism Spectrum Particles of light, called photons, each have a wavelength.

19-Oct-15 Physics 1 (Garcia) SJSU Newton’s Color Wheel Prism spectrum is a straight line, so why did Isaac Newton describe color using a circular wheel?

19-Oct-15 Physics 1 (Garcia) SJSU Additive Color Wheel Spectral Colors Not in the spectrum. How do we see these? R Y B G M C Red Yellow Green Cyan Blue Magenta

19-Oct-15 Physics 1 (Garcia) SJSU Adding Colored Lights Stream of red & green photons looks same as yellow photons (metamerism) Theatrical lighting or YELLOW Eye to Brain white Notice overlap of red, green, & blue is seen as white light

19-Oct-15 Physics 1 (Garcia) SJSU Demo: Seeing Yellow Sodium lamps emit yellow photons Color monitor can only emit red, green, and blue (RGB); creates other colors by selectively turning RGB pixels on or off.

19-Oct-15 Physics 1 (Garcia) SJSU Trichromatic Theorists Thomas Young ( ) English physicist Hermann von Helmholtz ( ) German physicist James Clerk Maxwell ( ) Scottish physicist

19-Oct-15 Physics 1 (Garcia) SJSU Simple Trichromatic Theory Yellow & Red photons excite me Yellow, Green & Cyan photons excite me Cyan & Blue photons excite me Inside your eye there are three receptors MOE CURLY LARRY

19-Oct-15 Physics 1 (Garcia) SJSU Trichromatic: Seeing Yellow Yellow & Red photons excite me. I’M EXCITED Yellow, Green & Cyan photons excite me. I’M EXCITED Cyan & Blue photons excite me. Yawn. Yellow seen when Curly and Larry excited, either by yellow photons or red & green photons. MOE CURLY LARRY

19-Oct-15 Physics 1 (Garcia) SJSU Trichromatic: Seeing Magenta Yellow & Red photons excite me. I’M EXCITED Yellow, Green & Cyan photons excite me. Yawn. Cyan & Blue photons excite me. I’M EXCITED Magenta is seen by eye when Moe and Larry excited, which no single type of photon can achieve. MOE CURLY LARRY

19-Oct-15 Physics 1 (Garcia) SJSU Demo: Maxwell Color Disk Disk painted half red, half blue looks magenta when rapidly spinning.

19-Oct-15 Physics 1 (Garcia) SJSU Mixing Blue & Red Paint Mixing paint or ink is different from adding colors together by light. Mix of blue and red paint produces a blackish brown

19-Oct-15 Physics 1 (Garcia) SJSU White Trichromatic: Seeing White Yellow & Red photons excite me. I’M EXCITED Yellow, Green & Cyan photons excite me. I’M EXCITED Cyan & Blue photons excite me. I’M EXCITED White seen when all three very excited Gray seen when all three less excited MOE CURLY LARRY

19-Oct-15 Physics 1 (Garcia) SJSU Trichromatic: Color Blindness Red, Yellow, Green & Cyan photons excite me. I’M EXCITED Cyan & Blue photons excite me. Yawn. MOE CURLY LARRY Color blindness occurs if the eye is missing one of the three receptors. Other receptors try to compensate but cannot distinguish some colors. Do I see red or green?

19-Oct-15 Physics 1 (Garcia) SJSU Color Blindness Classification Incidence (%) MalesFemales Anomalous Trichromacy Protanomaly (Red-cone weak) Deuteranomaly (Green-cone weak) Tritanomaly (Blue-cone weak) Dichromacy Protanopia (Red-cone absent) Deuteranopia (Green-cone absent) Tritanopia (Blue-cone absent) Rod Monochromacy (no cones) or 70? 21 or 74? Weakness or absence of one of the three types of cones is the cause of color blindness, leading to a reduced ability to distinguish colors.

19-Oct-15 Physics 1 (Garcia) SJSU Trichromatic: After-Image First stare at RED I’M EXCITED! Yawn. MOE CURLY LARRY Me too, but tired. ME TOO! I’M EXCITED! MOE CURLY LARRY Then stare at WHITE Moe and Curly are excited so what color is seen? CYAN (light blue-green)

19-Oct-15 Physics 1 (Garcia) SJSU Negative After-image Stare, unfocused, at the red cross for 10 seconds then look at white wall

19-Oct-15 Physics 1 (Garcia) SJSU Negative After-image Cyan

19-Oct-15 Physics 1 (Garcia) SJSU Negative After-image

19-Oct-15 Physics 1 (Garcia) SJSU Negative After-image Cyan Magenta Yellow

19-Oct-15 Physics 1 (Garcia) SJSU Simple Additive Color Wheel LARRY MOE CURLY Newton’s color wheel is a simple formulation of trichromatic theory. White

19-Oct-15 Physics 1 (Garcia) SJSU Color Vision in the Eye Three types of cones (color) One type of rod (B/W only)

19-Oct-15 Physics 1 (Garcia) SJSU CIE Hue-Saturation Diagram Eye is not a perfect optical instrument. Color “wheel” is actually distorted cone shape. Rim is full saturation, center is white LARRY % CURLY % 50% Larry 50% Curly 0% Moe 33% Larry 33% Curly 33% Moe

19-Oct-15 Physics 1 (Garcia) SJSU Spectral Reflectance Curves When white light shines on an object, some photons absorbed, others reflected by the object’s surface. White Red

19-Oct-15 Physics 1 (Garcia) SJSU Name That Color White Red Dark Brown (Burnt Sienna) BLUE GREEN RED 0% 100% BLUE GREEN RED

19-Oct-15 Physics 1 (Garcia) SJSU Name That Color Bluish Green Bright Yellow Blue (Cobalt) BLUE GREEN RED 0% 100% BLUE GREEN RED

19-Oct-15 Physics 1 (Garcia) SJSU Subtractive Color Absorbing filters or absorbing pigments remove colors from white light. Check Yourself: Yellow = Red + Green Cyan = Blue + Green Yellow & Cyan filters (or pigments) combine to give … Overlapping color filters

19-Oct-15 Physics 1 (Garcia) SJSU Check Yourself A soap film absorbs red, green, or blue light, depending on the film’s thickness. What colors do we see where red is removed? Where green is removed? Where blue is removed?

19-Oct-15 Physics 1 (Garcia) SJSU Four Color Printing Magenta Yellow Cyan Black Magenta + Yellow + Cyan All Four Green balloon printed with mix of yellow and cyan inks

19-Oct-15 Physics 1 (Garcia) SJSU Check Yourself Magenta Yellow Cyan Black Which inks are mixed for the bright red balloon and dark red dress?