Color and LightColor and Light

Intro question…. How is light different than normal waves??

Intro question…. How is light different than normal waves??

What is light? Wave or Particle

What is light? Wave or ParticleIs light a wave? (ENERGY)

YesIs light a bunch of particles? (Matter)

YesLight is unique, it is what we call an

Electromagnetic wave

Is light a wave? (ENERGY)Yes

Is light a bunch of particles? (Matter)Yes

Light is unique, it is what we call an Electromagnetic wave

How is light like a particle (matter)?

How is light like a particle (matter)?Does not need a medium to travel through

Can travel through a vacuum

high energy (intensity of light) does not effect light the same way as normal wavesEnergy associated w/ frequency rather than

amplitude

Light consists of Photons- massless bundles of concentrated electromagnetic energy

Photoelectric effectEjection of electrons from certain metals when

exposed to certain frequencies of light

Does not need a medium to travel throughCan travel through a vacuum

high energy (intensity of light) does not effect light the same way as normal wavesEnergy associated w/ frequency rather than

amplitude

Light consists of Photons- massless bundles of concentrated electromagnetic energy

Photoelectric effectEjection of electrons from certain metals when

exposed to certain frequencies of light

How is light like a wave?How is light like a wave?Light can diffract (bend around stuff)Cannot travel through polar filtersCan exhibit Doppler Effect (change freq. Depending

on motion of source)

Can interfere (constructive or destructive) and refract (bend when travelling between diff. Media)

Has no mass

We refer to all of this as the dual nature of lightThis means………. Light is special

Light can diffract (bend around stuff)Cannot travel through polar filtersCan exhibit Doppler Effect (change freq. Depending

on motion of source)

Can interfere (constructive or destructive) and refract (bend when travelling between diff. Media)

Has no mass

We refer to all of this as the dual nature of lightThis means………. Light is special

Electromagnetic WavesElectromagnetic WavesLight is the oscillation of electric and

magnetic fieldsShake an elctircally charged rod then

you will create an EM waveMust always have same speed…

otherwise Electric Field and Mag. Field would reinformce each other to infinity or destroy each other

Light is the oscillation of electric and magnetic fields

Shake an elctircally charged rod then you will create an EM wave

Must always have same speed… otherwise Electric Field and Mag. Field would reinformce each other to infinity or destroy each other

Many diff. Kinds of “light”Many diff. Kinds of “light” A wide spectrum of types of light that we call

Electromagnetic Radiation These include…… infrared, radio, ultraviolet,

gamma rays, microwaves, x-rays, & visible light All exhibit same exact characteristics but vary

b/c of wavelength & frequency All types travel at the same speed

at The speed of light….300,000,000 m/s We can only ‘see’ the small portion that is ‘visible light’ The rest is invisible to the human eye

A wide spectrum of types of light that we call Electromagnetic Radiation

These include…… infrared, radio, ultraviolet, gamma rays, microwaves, x-rays, & visible light

All exhibit same exact characteristics but vary b/c of wavelength & frequency

All types travel at the same speedat The speed of light….300,000,000 m/s

We can only ‘see’ the small portion that is ‘visible light’ The rest is invisible to the human eye

Electromagnetic SpectrumElectromagnetic Spectrum

http://www.youtube.com/watch?v=i8caGm9Fmh0&list=PL09E558656CA5DF76&safe=active

http://www.youtube.com/watch?v=i8caGm9Fmh0&list=PL09E558656CA5DF76&safe=active

Visible LightVisible Light Wavelength range From about 700 nm to 400 nm 1 nm= 1 x 10^-9 m Different colors have different wavelengths &

frequencies Infinite amount of different colors ROYGBIV

Wavelength range From about 700 nm to 400 nm 1 nm= 1 x 10^-9 m Different colors have different wavelengths &

frequencies Infinite amount of different colors ROYGBIV

Absence of Light??Absence of Light??Black or White??White is combination of all colors

of lightBlack is complete lack of light, all

colors have been taken awayBlack would be the absence of

Light!!

Black or White??White is combination of all colors

of lightBlack is complete lack of light, all

colors have been taken awayBlack would be the absence of

Light!!

Transparent MaterialsTransparent MaterialsGlass- natural vibration frequency in the U-V

rangeProduces large amplitudes and energy is lost as

heat UV light cannot travel through glass

Visible light vibrates electrons w/ smaller amplitude so less collisions and less transfer as heat. So light will be reemitted as light Time delay between absorbtions and reemissions

causes light to move more slowly through glass than through a vacuum

Glass- natural vibration frequency in the U-V rangeProduces large amplitudes and energy is lost as

heat UV light cannot travel through glass

Visible light vibrates electrons w/ smaller amplitude so less collisions and less transfer as heat. So light will be reemitted as light Time delay between absorbtions and reemissions

causes light to move more slowly through glass than through a vacuum

Opaque MaterialsOpaque Materials Most materials there is no reemission, and light

Energy is converted to Heat Vibrations of the electrons are not passed from atom

to atom through the bulk of the material; rather the electrons vibrate for short periods of time and then reemit the energy as a reflected light wave

Metals are opaque- free electrons will vibrate easily and reflects light…. This is why metals are shiny

Most materials there is no reemission, and light Energy is converted to Heat

Vibrations of the electrons are not passed from atom to atom through the bulk of the material; rather the electrons vibrate for short periods of time and then reemit the energy as a reflected light wave

Metals are opaque- free electrons will vibrate easily and reflects light…. This is why metals are shiny

ShadowsShadowsShadows formed where light cannot reachSharp shadows- close light sourceBlurry shadows- fuzzy on the outside, more

dark on the insideUmbra- total ShadowPenumbra- partial shadow… some light

blocked but other light fills in

Shadows formed where light cannot reachSharp shadows- close light sourceBlurry shadows- fuzzy on the outside, more

dark on the insideUmbra- total ShadowPenumbra- partial shadow… some light

blocked but other light fills in

ShadowsShadows

Polarization of LightPolarization of Light Light waves are transverse Electrons vibrate and create a wave in the

direction of the vibration polarized

Since the electrons vibrate in random directions normal light is not polarized

If light shines on a polarizing filter, only the light waves in the direction of the polarization axis can get through

If two filters overlap at right angles, no light can get through

Light waves are transverse Electrons vibrate and create a wave in the

direction of the vibration polarized

Since the electrons vibrate in random directions normal light is not polarized

If light shines on a polarizing filter, only the light waves in the direction of the polarization axis can get through

If two filters overlap at right angles, no light can get through

DispersionDispersionDispersion--the breaking up of light into its component colors when travelling through a prism

Why does it happendifferent wavelengths (colors) of light travel through a medium

at different speeds, the amount of bending is different for different wavelengths.

Violet (short ) is bent the most and red(long ) the leastshort wavelengths travel more slowly (lower frequency) through

a medium than longer ones doits colors can be separated (dispersed)

by this difference in behavior.

Dispersion--the breaking up of light into its component colors when travelling through a prism

Why does it happendifferent wavelengths (colors) of light travel through a medium

at different speeds, the amount of bending is different for different wavelengths.

Violet (short ) is bent the most and red(long ) the leastshort wavelengths travel more slowly (lower frequency) through

a medium than longer ones doits colors can be separated (dispersed)

by this difference in behavior.

PrismsPrismsAny transparent substance that

can separate colorsRed bent least, violet most

Any transparent substance that can separate colors

Red bent least, violet most

RecompositionRecomposition

Opposite of dispersionCombining of colors of light using a

lens or mirrors to form white lightNewton’s Disk exhibits

recomposition

Series of mirrors

Opposite of dispersionCombining of colors of light using a

lens or mirrors to form white lightNewton’s Disk exhibits

recomposition

Series of mirrors

Newtons DiskNewtons DiskWhen spun fast enough

all the colors will turn white

Utililizes the principle of persistence of visionHuman eye retains an

image for 1/30th of a second

Connection… wheels on tvFiber optic blinker

When spun fast enough all the colors will turn white

Utililizes the principle of persistence of visionHuman eye retains an

image for 1/30th of a second

Connection… wheels on tvFiber optic blinker

How we see things….Subtractive Theory of Light

How we see things….Subtractive Theory of Light

Keep taking away colors until you wind up w/ oneObjects absorb every color other than the color it

appears However, most colors we see are various combinations

of colorsEx. A blue shirt may reflect mostly blue, some purple,

maybe some green, depending on the shade it appersWhat happens when light goes through filtersObjects we see act like light filtersColors combine the same way that pigments/paints do

Keep taking away colors until you wind up w/ oneObjects absorb every color other than the color it

appears However, most colors we see are various combinations

of colorsEx. A blue shirt may reflect mostly blue, some purple,

maybe some green, depending on the shade it appersWhat happens when light goes through filtersObjects we see act like light filtersColors combine the same way that pigments/paints do

Subtractive Theory of Light

Subtractive Theory of Light

Filters & PigmentsFilters & Pigments

Why are objects different colors?

Why are objects different colors?Is a certain object always going to be a

certain color no matter what??Depends on what kind of light is hitting it

Is a certain object always going to be a certain color no matter what??Depends on what kind of light is hitting it

Additive theory of lightAdditive theory of lightAdd colors of light to each other until

one is madeSimple adding of different colors of

light, no filters involved• Ex. TVs, • projectors

Add colors of light to each other until one is made

Simple adding of different colors of light, no filters involved

• Ex. TVs, • projectors

Why does white light look white?Why does white light look white?

Additive v. Subtractive Color MixingAdditive v. Subtractive Color Mixing

Subtractive Primary Colors• Cyan- reflects green & blue• Yellow - reflects red & green• Magenta – reflects red & blue

– So if you overlap a red filter w/ a blue filter you will wind up with Magenta

When different colored spotlights overlap in a dark

room, additive mixing occurs. If the commonly used additive

primary colors red, green, and blue all overlap in effectively equal mixture, white light is

produced at the center. Additive color mixing is

conceptually simpler than the subtractive color mixing you get with paints and pigments since you are just adding light energy in different ranges of

the visible spectrum.

Additive color mixing with red, blue, and green

additive primary colors.

Additive and Subtractive Color Mixing AnimationsAdditive and Subtractive Color Mixing Animations

http://www.physics-chemistry-interactive-flash-animation.com/optics_interactive/additive_color_model_mixing_synthesis.htm

http://www.physics-chemistry-interactive-flash-animation.com/optics_interactive/subtractive_color_model_mixing_synthesis.htm

• Art class color wheel??

Colors of ObjectsColors of Objects

http://www.physics-chemistry-interactive-flash-animation.com/optics_interactive/colours_of_objects.htm

Complementary Colors• Two colors that will combine to make white

light• Negative images

– Will show the original colors complement – Red & cyan, blue & yellow, green & magenta