Seeing LightSeeing Light

StudStudents will be able toents will be able to

Describe parts of eyeDescribe parts of eye

Explain how vision problems occurExplain how vision problems occur

Identify uses of lightIdentify uses of light

Page 126Page 126

SightSight

Combination of eye capture light and Combination of eye capture light and brain working to understand imagesbrain working to understand images

125

Parts of EyeParts of Eye

ScleraSclera

White partWhite part

Many nervesMany nerves

Clear in frontClear in front

Cornea – Help to focus light into Cornea – Help to focus light into eyeeye

127

IrisIris

Eye ColorEye Color

Absorbs lightAbsorbs light

MuscleMuscle

Control PupilControl Pupil

Dilate when dark to get light inDilate when dark to get light in

Contract when bright to protect eyeContract when bright to protect eye

Important medical assessmentImportant medical assessment

Fixed and DilatedFixed and Dilated 127

LensLens

Focus lightFocus light

Ciliary MuscleCiliary Muscle

Controls shapeControls shape

Thin for farThin for far

Relaxes muscleRelaxes muscle

Thick for closeThick for close

Contracting muscleContracting muscle

Can cause eye fatigueCan cause eye fatigue127

RetinaRetina

Responds to lightResponds to light

Cone = ColorCone = Color

Rod = MotionRod = Motion

Poor designPoor design

127

Optic NerveOptic Nerve

Message to brainMessage to brain

Double image isDouble image is

merged in brainmerged in brain

Needs to turnNeeds to turn

image uprightimage upright

Creates blind spotCreates blind spot

127

NearsightednessNearsightedness

Can only see object that are nearCan only see object that are near

128

FarsightednessFarsightedness

Can only see object that are farCan only see object that are far

128

AstigmatismAstigmatism

Lens or cornea distortedLens or cornea distorted

128

Using LightUsing Light

Light from Nebula took 3 million yearsLight from Nebula took 3 million years

129

Optical InstrumentsOptical Instruments

TelescopesTelescopes

Use lenses to focus lightUse lenses to focus light

Big image to smallBig image to small

RefractingRefracting

Two convex lensesTwo convex lenses

Larger – ObjectiveLarger – Objective

Smaller – EyepieceSmaller – Eyepiece

130

Optical InstrumentsOptical Instruments

ReflectingReflecting

MirrorsMirrors

Concave MirrorConcave Mirror

Plane MirrorPlane Mirror

Convex lensConvex lens

130

MicroscopesMicroscopes

Small image and make bigSmall image and make big

Two lensesTwo lenses

Larger – ObjectiveLarger – Objective

Smaller – EyepieceSmaller – Eyepiece

131

CameraCamera

Lens to focus imageLens to focus image

onto film or screenonto film or screen

DiaphragmDiaphragm

Acts like pupil to let in lightActs like pupil to let in light

131

LaserLaser

FlashlightFlashlight

All colors of lightAll colors of light

LaserLaser (Light Amplification Stimulated Emission of Radiation)(Light Amplification Stimulated Emission of Radiation)

One type of lightOne type of light

Bounced by partial mirrorBounced by partial mirror

132

LaserLaser

Laser UsesLaser Uses

133

Laser UsesLaser Uses

HolographyHolographyPictures that appear to move when you movePictures that appear to move when you move

SurgerySurgeryCut tissue and seals blood vessels as you cutCut tissue and seals blood vessels as you cut

Much less bleedingMuch less bleedingThin tissue (lasik surgery)Thin tissue (lasik surgery)Welding (detached retina)Welding (detached retina)Destroy tissue (cancer or blemishes)Destroy tissue (cancer or blemishes)

134

Optical FibersOptical Fibers

Thin strands of glass/plasticThin strands of glass/plastic

Prevent laser light from escapingPrevent laser light from escaping

Total internal reflectionTotal internal reflection

136

Optical Fiber UsesOptical Fiber Uses

MedicineMedicine

Attached to camera see insideAttached to camera see inside

CommunicationCommunication

Each can carry thousands of Each can carry thousands of

phone conversationsphone conversations

137

QuizQuiz

HomeworkHomework

State the three problems that can go State the three problems that can go wrong with vision.wrong with vision.

QuizQuiz

1.1. What is the clear part of the eye?What is the clear part of the eye?a.a. CorneaCornea

b.b. IrisIris

c.c. PupilPupil

d.d. ScleraSclera

QuizQuiz

2. In bright light your pupil should be…2. In bright light your pupil should be…s. Smalls. Small

l. Largel. Large

QuizQuiz

3. What causes eye fatigue3. What causes eye fatiguea. Looking at an object far awaya. Looking at an object far away

b. Looking at an object up closeb. Looking at an object up close

QuizQuiz

4. What is wrong with this eye?4. What is wrong with this eye?a.a. FarsightedFarsighted

b.b. NearsightedNearsighted

c.c. AstigmatismAstigmatism

d.d. NothingNothing

QuizQuiz

5. Which telescope uses mirrors?5. Which telescope uses mirrors?a.a. RefractingRefracting

b.b. ReflectingReflecting

c.c. Neither oneNeither one

d.d. BothBoth

QuizQuiz

6. Which part of the camera controls the 6. Which part of the camera controls the amount of light that enters the camera?amount of light that enters the camera?

a.a. DiaphragmDiaphragm

b.b. LensLens

c.c. ShutterShutter

d.d. Shutter releaseShutter release

e.e. OtherOther

QuizQuiz

7. A laser always produces…7. A laser always produces…a.a. Many wavelengths of lightMany wavelengths of light

b.b. One wavelength of lightOne wavelength of light

c.c. Red lightRed light

d.d. Green lightGreen light

e.e. OtherOther

QuizQuiz

8. Which is not a function for lasers8. Which is not a function for lasersa.a. Bar code scannerBar code scannerb.b. CuttingCuttingc.c. Reading/Writing CDsReading/Writing CDsd.d. HologramsHologramse.e. SurgerySurgeryf.f. SurveyingSurveyingg.g. Viewing starsViewing stars

QuizQuiz

9. What prevents light from escaping a fiber 9. What prevents light from escaping a fiber optic cable?optic cable?

a.a. Total external reflectionTotal external reflection

b.b. Total internal reflectionTotal internal reflection

c.c. Light does escapeLight does escape

d.d. OtherOther

QuizQuiz

10. What is not a use for fiber optics?10. What is not a use for fiber optics?a.a. MedicineMedicine

b.b. Telephone serviceTelephone service

c.c. Television serviceTelevision service

d.d. All of the aboveAll of the above