Light & Color
Light:
Light that can be sensed by our eyes is Visible Light
Visible light consists of a continuous range of wavelengths or frequencies
Specific wavelengths correspond to a specific color based upon how we perceive light of that wavelength
Dispersion & Recomposition:
If a prism is placed in a beam of white light:
Dispersion occurs resulting in the ‘separation’ of light into a spectrum of colors
A type of refraction Refractive index varies with the wavelength or
color of light Lower the wavelength, higher the refractive index
Dispersion due to different refractive angles
How rainbows occur
Recomposition recombines the colors of the spectrum
When light strikes an object, the specific wavelengths can be absorbed or reflected
The wavelengths that are reflected by an object, cause the perceived color of the object
Ex.ROYGBIV
Capable of absorbing ROYBIV
G ROYBIV all absorbed by object
G reflected
Therefore object “appears” green
If all absorbed, then object appears black
If all reflected, then object appears white
What color will the objects appear to be?
ROYGBIV ROYGBIVROYGBIV
Capable of absorbing ROY
Capable of absorbing YGBIV
Capable of absorbing ROYGBIV
ROGBIVnothing BLACK
Viewing objects:
Objects may be viewed through filters &/or under different light
Causing the color of objects to be perceived differently
Recall white light is ROYGBIV
Filters will only allow specific colors of light (& the color on either side in the spectrum) to pass
Ex. ROYGBV
Blue Filter
G
BV
ROYGBV
Yellow Filter
O
YG
White light passes through a yellow filter. What color light will pass?
Recall colors are perceived b/c of the color of light reflected
Viewing objects under different color light will affect the perceived color since some colors may or may not be present to be reflected!!!
ROYGBV
Blue Filter
G
BV
A white dress is viewed under a blue filter. What color will the dress appear?
BLUE
ROYGBV
Green Filter
Y
GB
A yellow shirt is viewed under a green filter. What color will the shirt appear?
Yellow
ROYGBV
Yellow Filter
O
YG
A red shirt is viewed under a yellow filter. What color will the shirt appear?
BLACK
ROYGBV
A blue shirt is viewed under red light. What color will it appear?
BLACK
ROYGBV
A blue shirt is viewed under green light. What color will it appear?
BLUE
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Standing on a stage, a singer is illuminated by three lights, each emitting a different color.
When the first light is used, he appears to be wearing black shoes, red pants & a red shirtWhen the second light is used, he appears to be wearing blue shoes, black pants & a blue shirt
When the third light is used, he appears to be wearing black shoes, black pants & a green shirt
What color are the singer’s shoes, pants & shirt?
Shoes Pants Shirt
1st Light Blk Red Red
2nd Light Blue Blk Blue
3rd Light Blk Blk Green
-----
GBV
-----
Reflecting blue so….
Shoes are blue
RO
-----
-----
Reflecting all so…
Pants are red
RO
GBV
YGB
Reflecting red so…
Shirt is white
Red
Blue
Green
Color Addition:
White light is ROYGBIV but… White light can also be produced by
adding colors (or frequencies) Any three colors of light which produce
white light when combined are primary colors of light
RED, GREEN & BLUE
By adding primary colors of light, other colors can be produced
Ex.
TVs, computers, stage lights
Red Green
Blue
Yellow
CyanMagenta
White
25
26
27
Yellow Magenta Cyan
Any two colors of light which when mixed together in equal intensities produce white are complementary colors of eachother
Ex. Red & Cyan Blue & Yellow Green & Magenta
If magenta light and yellow light are added together, will white light be produced?
Magenta = Red & Blue
Yellow = Red & Green
Light will appear “light pink”
Color Subtraction:
Process of “removing” color Increasing absorption of colors and
decreasing reflection of colors Ex.
Paint pigments, printer ink
Pigment capable of absorbing blue light
R G B R G Blue absorbed
Red & Green Reflected
Therefore object “appears” yellow
Pigment capable of absorbing green light
R G B
R BGreen absorbed
Red & Blue Reflected
Therefore object “appears” magenta
What color would an object capable of absorbing green light appear?
Primary colors (pigments) of paint are cyan, magenta & yellow
Each primary color of paint absorbs one primary color of light
Cyan
Yellow
MagentaBlue
RedGreenCyan absorbs Red
Magenta absorbs Green
Yellow absorbs Blue