Light and Color

Light and Matter

• Objects can absorb, reflect and transmit light

• Opaque– Only absorbs and

reflects light– No light passes through

Light and Matter

• Translucent– Allows some light to

pass through

• Transparent– Allows most light

through– Absorbs and reflects

very little light

Reflection of Light

• Reflection– Light strikes an object

and bounces off

• Law of Reflection– Angle of incidence

(striking the object) is equal to angle of reflection (bouncing off the object)

Reflection of Light• Regular reflection– Smooth surfaces

produce sharp images

• Diffuse reflection– Very uneven surfaces

produce diffuse reflection

– Most surfaces are rough and produce diffuse reflection

Refraction of Light

• Refraction– Bending of light waves– Caused from a change in

speed– Larger index of

refraction, the more light has slowed down

Refraction

Refraction of Light

• Prisms– Separates light into

different colors– Amount of bending is

caused by wavelength– Red bend the least– Violet bend the most

Refraction of Light• Rainbows– Raindrops acts as a

prism

Refraction of Light

Refraction of Light

• Mirage– Image of a distant object

produced by the refraction of light

– Occurs because of different densities of air layers

– Light travels faster in warm air

– Slower in cool air

Mirage

Light and Color• White light is a blend of all colors of spectrum– ROY G BIV

• Red objects appear red because it reflects red and absorbs all other colors

• Green reflects green and absorbs all other colors

Light and Color

• Black– Is not a color present in

visible light

– Absorb all colors of the light spectrum

– Reflects little to no light back to our eyes

Colored Filters

• Filters– Transparent material

that transmits one or more colors of light but absorbs all other

– Color of filter is color of light it transmits

– Color Filters

Mixing Colors

• Pigment– Colored material used to

change color of other substances

– Examples• Paint• Dyes

Mixing Colored Lights• Primary Colors of Light

– Red– Green– Blue

• Mix these 3 in equal amounts, produces white light

• Mix in different proportions, all the colors we see

• Color Vision

Paint Pigments

• Mixing paint is different than mixing colors of white light

• Paints are made from colored pigments

• 3 primary pigments– Magenta (bluish-red)– Cyan (greenish-blue)– Yellow

Primary Pigments

• Mixing three primary pigments produces black

• Known as subtractive colors

Color and Vision

• Retina– Area on the inside of

your eyeball– Made of cone and rod

cells

• Rods– Sensitive to dim light– Night vision

• Cones– Allows us to see color

and detailed shapes

Cones

• 3 types of cones– Red

• Sensitive to red and yellow

– Green• Sensitive to yellow and

green

– Blue• Sensitive to blue and violet

Colorblindness

• Colorblindness– Caused by one or more

sets of cones not functioning correctly

– Can see color but can’t distinguish between certain colors

Color Blindness

• Vision simulator

Producing Light

• Incandescent Lights– Produces light by

heating piece of metal until it glows

– Tungsten– Used in most homes

Producing Light

• Fluorescent Lights– Bulbs filled with gas– Inside bulb coated with

phosphorus– Electrons collide with

gas and emit ultraviolet radiation

– Phosphorus absorb this radiation and give off light

Producing Light

• How fluorescent light bulb works

• Very energy efficient

Producing Light

• Neon Lights– Work similar to

fluorescent bulbs– Tubes filled with gas

(usually neon)– Other gases produce

different colors– Neon Lights

Producing Light

• Sodium-Vapor Lights– Used for streetlights and

outdoor lighting– Tube contains mixture of

argon gas, neon gas and sodium metal

– Emits yellow-orange glow

Producing Light

• Tungsten-Halogen Lights– Used to create very

bright light– Tube filled with tungsten

filament and a halogen gas

– Gas caused filament to get very hot