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