Now let’s focus on…Now let’s focus on… The visible spectrumThe visible spectrum

– Light and pigmentLight and pigment

Visible lightVisible light is that portion of the is that portion of theelectromagnetic spectrum which electromagnetic spectrum which stimulates the retina of thestimulates the retina of thehuman eye.human eye.

Visible spectrumVisible spectrumwavelengths rangewavelengths rangefrom about from about 400 nm400 nm (violet)(violet) to 760 nmto 760 nm (red)(red)..Light travels at about Light travels at about 3 x 103 x 1088 m/s m/s throughthroughempty space and slightly slower empty space and slightly slower through air.through air.

Remember that for all waves, Remember that for all waves, v = fv = f..

CCOOLLOORRMaterials may be classified as:Materials may be classified as:

transparenttransparent -- readily transmits light;readily transmits light;can clearly see objects through themcan clearly see objects through themtranslucenttranslucent - transmits, but diffuses, light;- transmits, but diffuses, light;

cannot see objects clearly through themcannot see objects clearly through themopaqueopaque - transmits no light;- transmits no light;

cannot see through themcannot see through them

WHITE light is a combination of ALL the colors of the visible spectrum.

RedRed, , orangeorange, , yellowyellow, , greengreen, , blueblue, , indigoindigo, , violetvioletis the order ofis the order of

increasing frequencyincreasing frequencyor or decreasing wavelengthdecreasing wavelength..

Frequencies directly above this spectrum areFrequencies directly above this spectrum areultravioletultraviolet..

Frequencies directly below this spectrum areFrequencies directly below this spectrum areinfraredinfrared..

Mixing colorsMixing colors There are There are twotwo ways to mix colors ways to mix colors

Mixing colors of Mixing colors of LIGHTLIGHT– Additive mixingAdditive mixing

Mixing colors of Mixing colors of PIGMENTPIGMENT– paint, ink or dyespaint, ink or dyes– Subtractive mixingSubtractive mixing

Mixing LightMixing Light Used in computer screens, TVs, and Used in computer screens, TVs, and

stage lightingstage lighting The primary colors are The primary colors are

– Red, Green and Blue Red, Green and Blue – ((RRoy oy GG. . BBiv)iv)

The secondary colors are The secondary colors are – Cyan, Magenta and YellowCyan, Magenta and Yellow

Mixing Light - AdditiveMixing Light - Additive

Mixing LightMixing LightYellow Magent

a

CyanWhite

• Complimentary colors are ACROSS from each other• Red-Cyan, Blue-Yellow, Green-Magenta• When complementary colors are mixed, they form white light.

Light – Additive ProcessLight – Additive Process Called “additive” process because new Called “additive” process because new

colors are formed by the addition of colors are formed by the addition of more than one color signal.more than one color signal.

The additive primary colors are RED, The additive primary colors are RED, GREEN, and BLUE.GREEN, and BLUE.

If the signal is equal parts red, green, If the signal is equal parts red, green, and blue we perceive this is white light.and blue we perceive this is white light.

Mixing Light - AdditiveMixing Light - Additive

Pigments – Subtractive Pigments – Subtractive ProcessProcess

• Dyes and pigments subtract out colors by absorbing some colors and reflecting others.

• The primary pigments are cyan, magenta, and yellow. These colors are the result of the absorption of one of the primary colors of light.

Pigments – Subtractive Pigments – Subtractive ProcessProcess

Pigments – Subtractive Pigments – Subtractive ProcessProcess

Black is made when no light is Black is made when no light is reflected. If you add magenta, cyan, reflected. If you add magenta, cyan, and yellow together, they absorb all and yellow together, they absorb all light so it looks black. light so it looks black.

To make green paint you need to To make green paint you need to absorb red and blue light and reflect absorb red and blue light and reflect green light. So you mix cyan, which green light. So you mix cyan, which absorbs red, and yellow, which absorbs red, and yellow, which absorbs blue.absorbs blue.

Making Green PaintMaking Green Paint

Mixing PigmentsMixing Pigments