LightLight

Electromagnetic RadiationElectromagnetic Radiation

Electromagnetic wavesElectromagnetic waves (E.M.) are (E.M.) are transverse waves produced by the motion transverse waves produced by the motion of electrically charged particles (of electrically charged particles (photonsphotons).).

E.M. waves do not require a medium, and E.M. waves do not require a medium, and are therefore able to travel at 186,000 mi/s are therefore able to travel at 186,000 mi/s (300,000 km/s),(300,000 km/s), the speed of light (which is the speed of light (which is an E.M. wave).an E.M. wave).

Electromagnetic SpectrumElectromagnetic Spectrum

The different electromagnetic waves are The different electromagnetic waves are arranged in the arranged in the electromagnetic electromagnetic spectrumspectrum in order of in order of increasing increasing frequency and decreasing wavelengthfrequency and decreasing wavelength..

The higher the frequency, the more The higher the frequency, the more photons (energy) per wave, and the photons (energy) per wave, and the more potentially harmful the wave is.more potentially harmful the wave is.

Low energyLow energy High energy High energy

Radio WavesRadio Waves Radio waves are the lowest Radio waves are the lowest

frequency E.M. wave.frequency E.M. wave. They are used primarily for They are used primarily for

communications, such as cell communications, such as cell phones, t.v. and radio phones, t.v. and radio transmissions, and cordless devices transmissions, and cordless devices such as phones, speakers, etc.such as phones, speakers, etc.

MicrowavesMicrowaves MicrowavesMicrowaves are a type of radio wave. They are are a type of radio wave. They are

used in cell phones and microwave ovens.used in cell phones and microwave ovens. At normal levels, microwaves are harmless.At normal levels, microwaves are harmless.

Infrared RadiationInfrared Radiation Infrared radiationInfrared radiation transfers energy in the transfers energy in the

form of heat. form of heat. Examples include heat lamps and the Examples include heat lamps and the

warmth from the sun. Special types of film warmth from the sun. Special types of film and cameras can show infrared radiation. and cameras can show infrared radiation. This is called This is called thermographythermography..

Ultraviolet Light (U.V.)Ultraviolet Light (U.V.)

U.V. rays are potentially dangerous at high U.V. rays are potentially dangerous at high levels or with prolonged exposure.levels or with prolonged exposure.

U.V. rays can cause sunburns and skin U.V. rays can cause sunburns and skin cancer, and kill bacteria and healthy cells.cancer, and kill bacteria and healthy cells.

The ozone layer of the The ozone layer of the atmosphere blocks most u.v. atmosphere blocks most u.v. rays from reaching the earth.rays from reaching the earth.

Using sunscreens with high Using sunscreens with high S.P.F. ratings can also help S.P.F. ratings can also help protect your skin from u.v. protect your skin from u.v. rays.rays.

X-RaysX-Rays X-rays are high frequency X-rays are high frequency

e.m. waves which are e.m. waves which are potentially dangerous at potentially dangerous at moderate levels. moderate levels.

X-rays can penetrate many X-rays can penetrate many materials such as skin, materials such as skin, muscle, and many fabrics.muscle, and many fabrics.

Visible LightVisible Light Visible light can be separated into 7 different Visible light can be separated into 7 different

colors. From lowest frequency to highest, they colors. From lowest frequency to highest, they follow the acronym ROY G. BIVfollow the acronym ROY G. BIV

When all 7 colors are combined together they When all 7 colors are combined together they produce white light.produce white light.

Prisms & RainbowsPrisms & Rainbows

PrismsPrisms: Separates white light into its component colors. The longer the wavelength, the less it will be bent by the prism.

RainbowsRainbows- light shining thru tiny droplets of water, each droplet acts as a prism

ColorColor The color of the object you see is the light that is

reflected from its surface. All other colors are absorbed by the object.

Primary & Secondary Light ColorsPrimary & Secondary Light Colors The 3 colors of light that can combine to form all other colors are primary primary

colorscolors – a. Red, Blue, Green i. Equal Red + Equal Blue = Magenta (secondary color) ii. Equal Red + Equal Green = Yellow (secondary color) iii. Equal Green + Equal Blue = Cyan (secondary color) iv. Equal Red + Equal Green + Equal Blue = White

MagentaYellow

Cyan

PigmentsPigments PigmentPigment – substance that color other materials like paints, inks, etc a. Primary Pigments are Cyan, Yellow & Magenta b. Cyan + Yellow + Magenta = Black c. Cyan + Yellow = Red d. Yellow + Magenta = Red e. Cyan + Magenta = Blue f. The primary pigments are the secondary light colors!

BlueRed

Green

Compare Lights & PigmentsCompare Lights & Pigments Three primary colors = three secondary pigments Three primary pigments = Three secondary colors

Transparent materialsTransparent materials allow allow almost all visible light to pass almost all visible light to pass through.through.

Ex.: glass, plastic wrapEx.: glass, plastic wrap

Translucent materialsTranslucent materials allow a partial allow a partial amount of visible light to pass through.amount of visible light to pass through.

Ex.: wax paper, shower doors, plastic milk Ex.: wax paper, shower doors, plastic milk jugsjugs

OpaqueOpaque materials stop almost all materials stop almost all visible light from passing through.visible light from passing through.

Ex.: drywall, thick curtainsEx.: drywall, thick curtains

Reflection & MirrorsReflection & Mirrors When light strikes an object It is either reflected, absorbed or

transmitted. Opaque: a material that reflects or

absorbs the light – can’t see through it. -wood

Transparent: The material transmits light – allows light to pass through it– glass

Translucent: allows some light to pass through – can’t see image clearly – wax paper, frosted glass.

Kinds of ReflectionsKinds of Reflections You see objects because light is reflected, bounced off of it. Law of Reflection: Angle of incidence equals the angle of

reflection– Angle coming in = angle going off

Regular Reflection: reflection off smooth surface – a mirror Diffuse Reflection: Irregular or bumpy, uneven surface – wall

RefractionRefraction RefractionRefraction of Light: BendBend or

change direction 1. As light rays enter a new

medium the cause light to bend 2. The denser the medium –

the slower the light travels 3. Index of RefractionIndex of Refraction: a

measure of how much a medium bends the light that travels through it.

4. The faster the beam, it will bend away from normal, the slower the beam, it will bend toward the normal.

3 Types of Mirrors3 Types of Mirrors Plane Mirror: a flat mirror – produces an image that is right side (virtual) up and the

same size as the original object – Concave Mirror: a mirror with a surface curved inward like a “cave” or a bowl.

Light reflected comes together to meet at a Focal Point. Can produce virtual or real images

Convex Mirrors: A mirror w/ a curved surface facing outward Reflected rays appear to come from a focal point behind the mirror Images formed are always Virtual

Concave mirror Convex mirror

Plane mirror

Real or Virtual?Real or Virtual? Image: a copy of an object formed by reflected or refracted light Virtual image: right side up appears to be coming from behind the

mirror. Real Image: is formed when reflected light rays actually meet at a

point. The image is upside down (inverted),

Lens – Concave & ConvexLens – Concave & Convex Lenses – a curved piece

of material used to bend light

Convex lensesConvex lenses: cause light passing through to bend toward the focal point.

• (converging)• The images produced

depends on the position of the object

Concave lensesConcave lenses: as light passes through, they are bent away from the center

• (diverging) • Images produced are only

virtual, not realConcave Lens

Convex Lens

Polarized LightPolarized Light

Normal light will produce waves which Normal light will produce waves which vibrate in many different planes.vibrate in many different planes.

Polarized lightPolarized light is light which vibrates in is light which vibrates in only 1 plane. This is created by passing only 1 plane. This is created by passing normal light through a polarized lens.normal light through a polarized lens.

Polarized lenses block all light waves except Polarized lenses block all light waves except those moving in 1 particular plane. those moving in 1 particular plane.

Polarized glass and lenses are effective at Polarized glass and lenses are effective at blocking out glare from the sun.blocking out glare from the sun.

As a result they are used in car windshields, As a result they are used in car windshields, sunglasses, and camera lenses.sunglasses, and camera lenses.

A A miragemirage is a visual distortion produced by is a visual distortion produced by the refraction of light.the refraction of light.

Some mirages produce a mirror or a watery Some mirages produce a mirror or a watery image, and others may make an object image, and others may make an object appear larger or smaller, nearer or further appear larger or smaller, nearer or further away.away.

This device produces a false image, but This device produces a false image, but not a true mirage.not a true mirage.

                                                                                                                                                                                                                                                                                                                                             

                                                                                       

I cdnuolt blveiee taht I cluod aulaclty I cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. The uesdnatnrd waht I was rdanieg. The phaonmneal pweor of the hmuan mnid. phaonmneal pweor of the hmuan mnid. Aoccdrnig to rscheearch at Cmabrigde Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh?wrod as a wlohe. Amzanig huh?

Vision - StructureVision - StructureNeed to know these structures & Need to know these structures &

their function:their function: Ciliary muscleCiliary muscle: ligaments : ligaments

attach the lens to these, they attach the lens to these, they contract & stretch the lens contract & stretch the lens allowing near & far focusallowing near & far focus

Vitreous humorVitreous humor: fluid inside : fluid inside eyeball maintains size & eyeball maintains size & shape of the eyeshape of the eye

RetinaRetina: contains the rods & : contains the rods & cones that are sensitive to cones that are sensitive to lightlight

Choroid coatChoroid coat: middle layer of : middle layer of the eyeballthe eyeball

ScleraSclera: the outer “whites of : the outer “whites of the eye”the eye”

Optic nerveOptic nerve: takes rod & : takes rod & cone impulse back to the cone impulse back to the occipital lobe for processingoccipital lobe for processing

Image Image ProcessingProcessing

FoveaFovea – – The central region where images focused is the fovea.

Rods Rods – about 1 billion, – about 1 billion, sensitive to brightness, sensitive to brightness, light and dark & light and dark & movementmovement

ConesCones – detect color, – detect color, about 3 million. 3 types about 3 million. 3 types of cones, sensitive to of cones, sensitive to red, blue & green red, blue & green wavelengths of light.wavelengths of light.

All rods & cones have All rods & cones have nerve fiber attached, nerve fiber attached, these collect at the back these collect at the back of the eye and form the of the eye and form the optic nerveoptic nerve which carries which carries the signal back to the the signal back to the eye.eye.

Lasers & Coherent LightLasers & Coherent Light Coherent lightCoherent light is visible light traveling at only 1 is visible light traveling at only 1

specific wavelength (resulting in 1 color). This specific wavelength (resulting in 1 color). This wave has all of it’s crests and troughs aligned and wave has all of it’s crests and troughs aligned and travels in only 1 direction. A laser is an example travels in only 1 direction. A laser is an example of coherent light.of coherent light.

A A laserlaser is a device used to create a is a device used to create a beam of coherent light.beam of coherent light.

LasersLasers

In a laser, an electric current excites a In a laser, an electric current excites a material (like neon) and causes it to material (like neon) and causes it to emit photons. These photons are emit photons. These photons are enclosed inside the laser device where enclosed inside the laser device where they bounce back and forth between 2 they bounce back and forth between 2 mirrors and becomes perfectly aligned mirrors and becomes perfectly aligned (coherent light).(coherent light).

Some of these photons, if they are aligned Some of these photons, if they are aligned correctly, escape through a small portion of correctly, escape through a small portion of one of the mirrors. This is the laser beam.one of the mirrors. This is the laser beam.