SpeedofLightQuestions

1. TheaveragedistancefromthesuntotheEarthis1.50×108km.Howlong(inminutes)doesittakeforsunlighttoreachtheEarth?

2. LightfromtheplanetUranustakes242min.toreachtheEarth.CalculatethedistancefromtheEarthtoUranus.

3. Incommunicatingwithanautomaticspacestation,radiosignalstravelingatthespeedoflightmusttraveladistanceof8.7×109meachway.Howlongdoesittakeforaradiosignaltotraveltothestationandback?

4. Alightyearisthedistancethatlighttravelsinoneyear.Howfar(inmeters)doeslighttravelin3.00years?

5. Onenanosecond(ns)is10-9s.Howfar,inmeters,doeslightactuallytravelin1.0ns?6. Thedistancetothemooncanbefoundwiththehelpofmirrorsleftonthemoonby

astronauts.ApulseoflightissenttothemoonandreturnstoEarthin2.562s.Usingthedefinedspeedoflight,calculatethedistancetothemoon.

7. Radiostationsareusuallyidentifiedbytheirfrequency.OneradiostationinthemiddleoftheFMbandhasafrequencyof99.0MHz.Whatisitswavelength?

8. Violetlighthasawavelengthof4.10x10-12m.Whatisthefrequency?9. Greenlighthasafrequencyof6.01x1014Hz.Whatisthewavelength?10. Whatisthewavelength(inmeters)ofaelectromagneticwavewithafrequencyof

640kHz?ANSWERS1. 8.33mins 2. 4.36x1012m 3. 58s4. 2.84x1016m 5. 0.30m 6. 3.84x108m7. 3.03m 8. 7.32x1019Hz 9. 4.99x10-7m10. 470m

RefractionandSnell’sLaw1. Lighttravelsthroughaliquidat2.50x108m/s.Findtheindexofrefractionofthat

liquid? 2. Whatisthespeedoflightinasubstancethathasanindexofrefractionof2.42?

Whatisthatsubstance? 3. Whatistheangleofrefractionwhenlightpassesfromairintodiamondatanangle

ofincidenceof60.0°?4. Lightpassesfromairintoanothersubstancethathasanindexof1.30.Iftheangleof

refractionis45.0°,thenwhatistheangleofincidence? 5. Amysteryobjectisinatankofwater.Alightbeaminthewaterstrikesthesurface

oftheobjectatanangleof42.2˚andrefractsintoitanangleof27.7˚.Findtheindexofthemysterysubstance.Whatmightthesubstancebe?

6. Whatisthespeedoflightinamediumiftheangleofincidenceinairis63ºandtheangleofrefractionis38º?

7. Atwhatangleofincidenceistherenorefraction? ANSWERS1. 1.20 2. 1.24x108m/s 3. 21.0˚4. 66.8˚ 5. 1.92 6. 2.07x108m/s7. 0˚

Refraction,TIRandCriticalAnglePractice

1. Medium1hasanindexofrefractionof1.20.Medium2hasanindexofrefractionof2.65.IfalightraypassesfromMedium2intoMedium1,willitberefractedtowardsorawayfromthenormal?

2. HowfarinkmwouldlighttravelinMedium1(fromquestion1)inthe2.0minutesthatittakesyoutocompletethisquestion?

3. Findthecriticalangleforadiamondinair.

4. Findthecriticalangleforadiamondinwater.

5. Alightrayinadiamondstrikethesurfaceatanangleof25˚.Findtheangleofrefractionifthediamondisinair.

6. Thecriticalangleforatypeofplasticis37.8˚.Findtheindexofrefractionofthatplasticandthespeedoflightintheplastic.

7. Thecriticalangleforafibreopticcableis24.624˚.Howlongwouldittakelighttotravelthrougha0.500kmlengthofthiscable?

8. Alightrayinwaterstrikesthesurfaceofcrownglassatanangleof79.4°tothenormal.Findtheangleofrefractioninsidetheglass?

9. Lighttravelinginflintglassstrikesaboundarywithanunknownsubstanceatanangleof65.2°.Thelightrefractstoanangleof71.6°intheunknownsubstance.Findtheindexandidentityoftheunknownsubstance.

10. Lighttravelinginethanolstrikesamysterysubstanceatanangleof78.0°tothenormal.Thelightisrefractedtoanangleof56.0°tothenormal.Whatisthespeedoflightinthemysterysubstance?

11. Lighttakes6.875x10-10stotravelthrougha12.5cmthickblockofplastic.Ifalightrayinairstrikestheblockatanangleofincidenceof32.5°,whatwouldtheangleofrefractionbeintheblock?

ANSWERS1. Away 2. 3.0x1010m 3. 24.4˚4. 33.3˚ 5. ??? 6. 1.63,1.84x108m/s7. 4.00x10–6s 8. 59.3° 9. 1.5410. 1.87x108m/s 11. 19.0°

Investigation:RefractionofLight–AirintoGlassProblem:Howislightrefractedwhenitpassesfromairintoanopticallydensermedium,likeglass?Materials:raybox(single-slit),semi-circularglassblock,polarco-ordinatepaperProcedure:

1. Placetheglassblockonthepolarco-ordinatepaperasshowninthepicture.Notethatthe0°lineactsasthenormalandshouldpassalongtheflatsurface.

2. Directasinglerayoflightattheflatsurfaceoftheglass,alongthenormal.Makeabsolutelysurethattheraypassesthroughthecenteroftheflatsurface.Measuretheangleofrefraction,andrecorditinthechartbelow.

3. Repeattheprocedureforanglesofincidenceof10°,20°,30°,40°,50°,and60°makingsuretorecordyourresultsinthechart.

4. Usingyourcalculator,determinethevaluesofthesinesofanglesofincidenceandrefraction.

5. Calculatetheratioofsini/sinRforeachpairofangles.Observation Angleof

Incidence(i)Angleof

Refraction(R)sini sinR sini/sinR

1 0° 2 10° 3 20° 4 30° 5 40° 6 50° 7 60°

Questions:

1. Whenlighttravelsfromairintoglasswithanangleofincidenceof0°,whathappenstoit?

2. Whenlighttravelsfromairintoglassatanangleofincidencegreaterthan0°,howisbentinrelationtothenormal?

3. Wherearetheincidentandrefractedrayslocatedinrelationtothenormal?

4. Howdoestheangleofrefractioncomparewiththeangleofincidenceineachcase?

5. Whatdoyounoteabouttheratioofsini/sinRforallcaseswheretheangleofincidenceis

>0°?

6. Iflighttravelsfromglassintoair,howdoyouthinkitwillbendinrelationtothenormal?

Investigation:RefractionofLight–GlassintoAirProblem:Howislightrefractedwhenitpassesfromglass(moredense)intoair(lessdense)?Materials:raybox(single-slit),semi-circularglassblock,polarco-ordinatepaperProcedure:

1. Placetheglassblockonthepolarco-ordinatepaperasshowninthepicture.Notethatthe0°lineactsasthenormalandshouldpassalongtheflatsurface.

2. Directasinglerayoflightatthecurvedsurfaceoftheglass,alongthenormal.Makeabsolutelysurethattheraypassesthroughthecenteroftheflatsurface.Measuretheangleofrefractionintheairandrecorditinthechartbelow.

3. Repeattheprocedureforanglesofincidenceof10°,20°,30°,40°,50°,and60°makingsuretorecordyourresultsinthechart.

4. Usingyourcalculator,determinethevaluesofthesinesofanglesofincidenceandrefraction.

5. Calculatetheratioofsini/sinRforeachpairofangles.6. Checktoseeatwhatangleofincidencetherefractedrayisat90°.

Observation Angleof

Incidence(i)Angleof

Refraction(R)sini sinR sini/sinR

1 0° 2 10° 3 20° 4 30° 5 40° 6 50° 7 60°

Questions:

1. Howwaslightrefractedwhentheangleofincidencewas0°?

2. Whenlighttravelsfromglassintoairatanangleofincidencegreaterthan0°,howisbentinrelationtothenormal?

3. Whichangleisalwaysgreater,theangleofincidenceortheangleofrefraction?

4. Wherearetheincidentandrefractedrayslocatedinrelationtothenormal?

5. Whatwastheaveragevalueofthesini/sinRrelationship?(ignorewhenθi=0°)

6. Whatistherelationshipbetweenthisvalueandthevaluefromstep5inthepreviouslab?

7. Whyistherenorefractionatthecurvedsurfaceinallcases?

8. Aboveapproximately45°,whathappenstoallthelight?

9. Atwhatangleofincidenceistheangleofrefraction90°?Determinethisvalue

mathematicallyaswellasexperimentally.

Investigation:ImagesFormedbyaConvergingLensProblems:1.Whatarethecharacteristicsandlocationsoftheimagesformedbyanobjectat

variouspositionsinfrontofaconverginglens? 2.Isthemirrorequationvalidforlenses?Materials:opticalbench,converginglens,lightsource,screenProcedure:1.Usethelenstofocusthelightfromadistantlightsourceontoascreen.Carefully

measurethefocallengthofthelensincentimeters.Turnthelensaroundandseeifitaffectsthefocallength.

2.Usingthevalueofthefocallengthinstepone,calculatethefollowingobjectdistances:2.5f,2.0f,1.5f,1.0f,and0.5f.Makeatablesimilartotheonebelowandrecordyourvalues.

3.Placethelensintheexactcenterofyouropticalbench. 4.Placethelightsourceat2.5f.Movethescreenuntilyoucaptureaclear,focused

imageonit.Recordtheimagedistanceandthecharacteristicsoftheimage. 5.Repeatstepfourfortheotherobjectdistances.Lookintothelensandviewthe

realimages.At0.5fyouwillnotbeabletoobtainanimageonthescreen.Lookintothelensforit.

ObjectDistance

ImageDistance

Characteristics 1𝑑𝑜

1𝑑𝑖

!!"+ !

!"

size attitude type2.5f= 2.0f= 1.5f= 1.0f= 0.5f= AnalysisQuestions1. Howdothefocallengthsforthetwosidesofthelenscompare?2. Astheobjectmovedfrom2.5ftowards1.0f,whathappenedtothe:

a. thesizeoftheimage?b. theimagedistance?c. theattitudeoftheimage?

3. Atwhatdistanceisitdifficulttoobtainaclearlyfocusedimage?4. Wherewouldyouplaceanobjectinrelationtothefocalpointtoobtain:

a. arealimage?b. avirtualimage?c. noimage

5. Determinethevalueof!!.Howdoesitcompareto !

!"+ !

!"forthefirstthreecases?

TheCowEyeDissectionLabWhatarethestructuresofthemammalianeyeandhowdotheyfunction?Themammalianeyeconsistsofmanyspecializedcellsandtissuesthatmakeupseveraldifferentstructures.Thestructureshavecertainfunctionsandtogether,theyformimagesthatareinterpretedbythebrain.Inthisinvestigation,youidentifythestructuresofacoweyeandlearntheirfunctions.ExternalfeaturesoftheeyeA.Locatethecornea,sclera,andopticnerve.

a. Thewhitepartoftheeye,thesclera,isatough,outercoveringoftheeyeball.Thescleragivestheeyeitsshapeandhelpstoprotectthedelicateinnerparts.

b. Thebluecoveringoverthefrontoftheeyeisthecornea.Whenthecowwasalive,thecorneawasclear.Togetherwiththelens,thecornearefractslightandhelpstheeyetofocus.Thecorneagivesalargercontributiontothetotalrefractionthanthelens.Thecurvatureofthecorneaisfixedwhilethatofthelensischangeable.Inyourcow’seye,thecorneamaybecloudy.

c. Youmaybeabletolookthroughthecorneaandseetheiris,thecoloredpartoftheeye,andthepupil,thedarkovalinthemiddleoftheiris.Atthebackoftheeyeistheopticnerve.Toseetheseparatefibersthatmakeuptheopticnerve,pinchthenervewithapairofscissorsoryourfingers.Ifyousqueezetheopticnerve,youmaygetsomewhitegoop.Thatismyelin,thefattylayerthatsurroundseachfiberofthenerve.Itisthenervethattransmitsvisualinformationfromtheeyetothebrain.

B.Examinethefatandmusclesurroundingtheeyeball.a. Withoutmovingyourhead,lookup.Lookdown.Lookallaround.Sixmusclesattachedtoyoureyeballmove

youreyesoyoucanlookindifferentdirections.Cowshaveonlyfourmusclesthatcontroltheireyes.Theycanlookup,down,left,andright,buttheycan’trolltheireyeslikeyoucan.Locatetheexternallyattachedmuscles.Thesemusclescontroleyemovementandhelpfocusimages.

b. Althoughthemusclesofeachindividualeyeworkasateam,theeyesthemselvesdonotfocusorworktogetheruntilmonthsafterbirth.However,oneeyeremainsdominant.Formacirclewithyourthumbandindexfinger.Holdthatpositionandplaceyourhandinfrontofyou.Withbotheyes,lookatsomethingthroughthecircle.Continuetoholdthatpositionandcloseoneeye;thenopenit.Closetheothereye.Theeyewhichisstillabletoviewtheobjectthroughthecircleisyourdominanteye.

c.Ifyoureachupandfeelaroundyoureye,you’llfeeltheboneofyourskull.There’syellowfatsurroundingyoureyeballtokeepitfrombumpingupagainsttheboneandgettingbruised.

C.Cutawaythefatandmuscle.D.Removethecornea–Usethephotosontheplacemattohelpyou.a. Useascalpeltomakeanincisioninthecornea.(Careful—don’tcut

yourself!)Cutuntiltheclearliquidunderthecorneaisreleased.Thatclearliquidistheaqueoushumor.It’smadeofmostlyofwaterandkeepstheshapeofthecornea.

b. Usethescalpeltomakeanincision(cut)throughthesclerainthemiddleof the

eye.

c. Useyourscissorstocutaroundthemiddleoftheeye,cuttingtheeyeinhalf.You’llendupwithtwohalves.Onthefronthalfwillbethecornea.Thecorneaismadeofprettytoughstuff—ithelpsprotectyoureye.Italsohelpsyouseebybendingthelightthatcomesintoyoureye.

d. Onceyouhaveremovedthecornea,placeitontheboard(orcuttingsurface)andcutitwithyourscalpelorrazor.Listen.Hearthecrunch?That’sthesoundofthescalpelcrunchingthroughlayersofcleartissue.Thecow’scorneahasmanylayerstomakeitthickandstrong.Whenthecowisgrazing,bladesofgrassmaypokethecow’seye—butthecorneaprotectstheinnereye.

E.Thenextstepistopullouttheiris.a. Theirisisbetweenthecorneaandthelens.Itmaybestucktothecorneaoritmayhavestayedwiththe

backoftheeye.Findtheirisandpullitout.Itshouldcomeoutinonepiece.b. Youcanseethatthere’saholeinthecenteroftheiris.That’sthepupil,theholethatletslightintotheeye.

Theiriscontractsorexpandstochangethesizeofthepupil.Indimlight,thepupilopenswidetoletlightin.Inbrightlight,thepupilshutsdowntoblocklightout.

c. Thebackoftheeyeisfilledwithaclearjelly.That’sthevitreoushumor,amixtureofproteinandwater.It’sclearsolightcanpassthroughit.Italsohelpstheeyeballmaintainitsshape.Thevitreoushumorisattachedtothelens.

F.Nowyouwanttoremovethelens.a. It’saclearlumpaboutthesizeandshapeofasquashedmarble. Thelensis

atransparentstructureintheeyethat,alongwiththecornea, helpstorefractandfocuslight.

b. Aringoftinyciliarymuscles,locatedalongtheinnersideofthe iris,connectsthelenstothemiddlelayeroftheeye.Ciliarymuscles contracttochangethecurvatureofthelens.

c. Thelensofthecow’seyefeelssoftontheoutsideandhardinthe middle.Holdthelensupandlookthroughit.Inalivingorganism,itiscompletelytransparent.(Youcowlensmaynotbetransparent.)Tofocusoncloserobjects,itgetsfattersoitcanrefractmorelight.

d. Putthelensdownonanewspaperandlookthroughitatthewordsonthepage.Ifyourlensistransparent,itshouldmagnify.

G.Nowit’stimetoexaminetheretina.a. Ifthevitreoushumorisstillintheeyeball,emptyitout.b. Ontheinsideofthebackhalfoftheeyeball,youcanseesome blood

vesselsthatarepartofathinfleshyfilm.Thatfilmistheretina. Beforeyoucuttheeyeopen,thevitreoushumorpushedagainsttheretinaso thatitlayflatonthebackoftheeye.Itmaybeallpushedtogetherinawad now.

c. Theretinaismadeofcellsthatcandetectlight.Theeye’slens usesthelightthatcomesintotheeyetomakeanimage,apicturemadeof light.Thatimagelandsontheretina.Thecellsoftheretinareacttothelightthatfallsonthemandsendmessagestothebrain.

d. Useyourfingertopushtheretinaaround.Theretinaisattachedto thebackoftheeyeatjustonespot.Canyoufindthatspot?That’stheplace wherenervesfromallthecellsintheretinacometogether.Allthesenervesgo outthebackoftheeye,formingtheopticnerve,thebundleofnervesthatcarries messagesfromtheeyetothebrain.Thebrainusesinformationfromthe retinatomakeamentalpictureoftheworld.

e. Thespotwheretheretinaisattachedtothebackoftheeyeiscalledtheblindspot.Becausetherearenolight-sensitivecells(photoreceptors)atthatspot,youcan’tseeanythingthatlandsinthatplaceontheretina.

H.Checkoutthetapetum.a.Undertheretina,thebackoftheeyeiscoveredwithshiny,blue-green stuff.Thisisthetapetum.Itreflectslightfromthebackoftheeye.Haveyoueverseen acat’seyesshiningintheheadlightsofacar?Cats,likecows,haveatapetum.Acat’s eyeseemstoglowbecausethecat’stapetumisreflectinglight.Ifyoushinealightata cowatnight,thecow’seyeswillshinewithablue-greenlightbecausethelight reflectsfromthetapetum.Humansdonothavethistapetum.I.Findyourblindspot.a.Tofindyourblindspot,usethetwodotsbelow.Holdonehandoveryourlefteyeandlookdirectlyattheleft-handdot.Atfirst,youcanseebothdotseventhoughyou'relookingdirectlyatonlyone.Asyouslowlymovethepageclosertoyoureyes,theright-handdotdisappears!Ifyoumoveyoureye,thedotwillreappear,butaslongasyoufocusonthefirstdot,thesecondwillbeinvisible.Moveevencloserandthemissingdotreappears.You’vefoundyourblindspot!

PW3Review

1.ThedistancefromSaskatoontoLucerne,Switzerlandis4575.2miles.Howlongwouldittakelighttotravelthere?2.UsainBoltranthe100mracein9.58seconds,fasterthananyotherhuman.Howfarwouldlighttravelinthattime?

3.Bluelighthasawavelengthof470nm.Whatisthefrequency?4.Yellowlighthasafrequencyof525THz.Whatisthewavelength?5.Lighttravelsthroughaliquidat2.81x108m/s.Findtheindexofrefractionofthatliquid?6.Whatisthespeedoflightinasubstancethathasanindexofrefractionof1.93?7.Whatistheangleofincidencewhenlightpassesfromairintodiamondwithanangleofrefractionof23.5°?8.Whatisthespeedoflightinamediumiftheangleofincidenceinairis24.0ºandtheangleofrefractionis19.8º?9.Findthecriticalangleforlighttravellingfromadiamondintowater.10.Thecriticalangleforanunknownsubstanceis42.3˚.Findtheindexofrefractionofthatsubstanceandthespeedoflightinthesubstance.

11.Thecriticalangleforanacrylicblockis41.3˚.Howlongwouldittakelighttotravelthrougha3.50cmblock?12.Lighttravels2.15x108m/sinanunknownsubstance.Ifalightrayinairstrikestheblockatanangleofincidenceof24.9°,whatwouldtheangleofrefractionbeintheblock?

13.Anobjectis3.0cmfromaconvexlensanditproducesavirtualimagethatis4.5cmfromthelens.Calculatethefocallength?

14.Themagnificationofaconverginglensis-0.45X.Ifanobjectis5.8cmtallandisplaced15.0cmfromthelens,calculatetheimageheightanddistance.

15.Ifanimageisproduced3.5cmfromadiverginglensthathasafocallengthof6.0cm,calculatetheobjectdistance.Iftheimageis0.75cmtall,whatistheobjectheightandmagnification?

16.Drawthefollowingtofindimagecharacteristicsinaconverginglens:a.f=4.0cmdo=7.5cmho=1.0cmb.f=3.5cmdo=7.0cmho=1.5cmc.f=6.5cmdo=3.0cmho=1.0cm17.Drawthefollowingtofindimagecharacteristicsinadiverginglens:a.f=4.0cmdo=7.5cmho=1.0cmb.f=7.0cmdo=7.0cmho=1.5cm18.Definethefollowingpartsoftheeye:

Ciliarymuscle Lens PupilSclera Opticnerve BlindspotVitreoushumour Aqueoushumour RetinaIris Cornea RodsCones

ANSWERSTONUMERICALQUESTIONS1.0.0244s 2.2.87x109m 3.6.4x1014Hz 4.5.71x10-7m5.1.07 6.1.55x108m/s 7.74.7° 8.2.50x108m/s9.33.3° 10.1.49;2.02x108m/s 11.1.77x10-10s12.17.6° 13.9.0cm 14.-2.6cm;6.8cm 15.8.4cm;1.8cm;0.42X16a.Real,inverted,larger b.Real,inverted,samesize c.Virtual,erect,larger17a.Virtual,erect,smaller b.???