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