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Color
White is the combination of all colors
Spectrum
• Sunlight can be split into its component colors• Called the color spectrum (Roy G. Biv)
Red Orange Yellow Green Blue Indigo Violet
Spectrum
Black and White
• White is the presence of all colors of light
• Black is the absence of any color of light
Color by Reflection
• Light energy can be absorbed by a surface
• electrons in the surface atoms vibrate
• generally some frequencies of light are absorbed while others are reflected
• this gives color to objects when illuminated by white light
• The color of the object will depend on the color of the light
Color by Transmission
• color of a transparent object depends on the color of light it transmits
• pigments absorb some light and transmit others
• glass transmits all visible colors
• a blue glass transmits only blue and absorbs all other color
Sunlight
• brightest in the yellow green area
• less bright in red and violet regions
Mixing colored light
• red + green + blue = white
• red + green = yellow• red + blue = magenta• green + blue = cyan• additive primary colors
red: lowest frequency green: middle frequency blue: highest frequency
http://www.hal-pc.org/~clement/Simulations/Mixing%20Colors/rgbColor.html
http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=11&CFID=822684&CFTOKEN=35660268
Mixing Pigments
• mixing pigments is different than mixing colored light
• paints contain small particles of pigments
• pigments reflect some wavelengths of light and absorb others
Color mixing by subtraction
• colors can be mixed together to make any color when printed on white paper
• subtractive primary colors magenta yellow cyan
Blue Sky
• oxygen and nitrogen molecules scatter light
• violet and blue light are scattered the most
• without an atmosphere, the sky would be black
• clouds (water droplets of broad range of sizes) scatter all visible light making them bright white
Red Sunrise
• Red is scattered the least
• Sun must go through more atmosphere at dawn and dusk
• Red light makes it through the thicker atmosphere at dawn and sunset
Blue water
• water absorbs infrared light
• water absorbs some red light
• in deeper water, no red makes it through
• without red, light looks greenish blue (cyan)
• we see this greenish blue color through the clear water
Light fingerprint
• every element emits a specific group of wavelengths of light
• called atomic spectra• can be used to
identify the nature of materials