Can I Believe My Eyes?blogs.4j.lane.edu/macwilliam/files/2019/09/PS1-Barbs-Version-2019-20.pdfOpCcal illusions can be fun because they fool you. OpCcal illusions are a kind of trick

Name:________________________________________________Period:___________

CanIBelieveMyEyes?

PhysicalScience1

Lightwaves,theirrollinsightandinteracAonswithmaBer

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Vocabulary DefiniAons/Images

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ScienAficPrinciples

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Lesson2–WhatcanopAcalillusionsteachus?Lesson2.1–Whatisgoingonwiththesepictures?

Whatwasthepointofthelastunit?

Whatwillwedo?Wewillobservetwostrangeimages.Bytheendoftheunit,wewillbeabletoex-plainhowtheseimageswork.

ProcedureLookatthefirstimageyourteacherprojects.Whatdoyousee?RecordyourobservaConsinthedatatable.Yourteacherwillprojectasecondimage.Whichsquareappearsdarkertoyou,squareAorsquareB?Recordwhatyouseeinthedatatable.Yourteacherwillmakesomechangestothesecondimage.Whichsquareappearsdarkernow,squareAorsquareB?RecordyourobservaCons.

Data

Conclusion

1. WhatdidyounoCceaboutthecirclesinthefirstimage?

2. Doyouthinkwhathappenedwasreal?Howdoyouknow?

Image Observations

First Image

Second Image

Second Image after masks

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3. WhydoyouthinkthatsquareAandsquareBlookeddifferentthefirstCmeyoulookedatthemthantheydidthesecondCmeyoulookedatthem?

4. AskingandexploringtheanswerstoquesConsisimportanttoscience.DoesthisacCvitymakeyouthinkofanyquesConsaboutlightoraboutthingsyousee?ListyourquesConsinthefollowingspace.

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Reading2.2–LookatThis

Ge`ngReadyThepictureshowstwobentrectangles.Whichbentrectangleislonger?Nowusearulertomeasurethesizeofthetwobentrectangles.Wereyoucorrect?Tomostpeople,BlookslongerthanA.Whenyoumeasured,youmighthavelearnedthatyourguesswaswrong.Inthisreading,youwilllearnhowyourbraincangetconfusedbywhatyoureyessee.Youwillbeabletocomparethefiguresinthisreadingtowhatyousawinclass.Tocomparemeanstothinkaboutwhatisalikeandwhatisdifferent.Asyouread,thinkaboutwhatissimilaranddifferentaboutthelightboxandthepicturesinthisreading.WhatAreOpAcalIllusions?Lookatthesepictures.Stareatthesmalldotinthecenterofthecircles.Nowmovethepictureclosertoyouwhileyoukeeplookingatthedot.Whathappens?TrickslikethesearecalledopCcalillusions.OpCcalisawordrelatedtoyoursenseofsight.Manyotherwordsstartwiththeprefixopt-.Anoptometristisaneyedoctor.Ifyouneedglasses,anopCcianmayhavehelpedyouchooseyourglasses.Youmayhaveseenmagicianswhoperformillusions.Magiciansdonotreallymakethingsdisappear.Buttheydoknowhowtofoolyourbrainsoyouthinkthingsdisappear.OpCcalillusionscanbefunbecausetheyfoolyou.OpCcalillusionsareakindoftrick.Youreyesplayanimportantroleinseeing.Butyoureyesandyourbrainworktogether.Yourbrainistheorganthatmakessenseofwhatyousee.InthepictureintheGeengReadingsecCon,youreyesseetwoidenCcalbentrectangles.Youreyesseetherightthing,butyourbraininterpretsitwrong.Whenyourbraingetsitwrong,thisiscalledanillusion.OpCcalillusionsandmagician’stricksarenotreal.Yourbrainisjustfooled.AnotherOpAcalIllusionLookatthesesmalldarksquares.Ifyoulookcloselyforafewseconds,youwillseelightgraycirclesinbetweenthesquares.Arethegraycirclesreallythere,ordotheyjustseemtobethere?Thisisanotherexampleofanillusion.Yourbrainisbeingfooledagain.CanYouFigureThisOut?HereisonemoreinteresCngimage.LookatthelinesseparaCngtherowsofblackandwhitesquares.Doyouthinkwhatyouareseeingisanillusion?Arethelines

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actuallyparallelandyourbrainisbeingfooled,orarethelinesreallyatangles?WeretheImagesinClassOpAcalIllusions?Inclass,yousawstrangeimages.Thefirstlookedlikeabunchofspinningcircles.ThesecondimagelookedlikeacheckerboardwithasquaremarkedAbeingclearlydarkerthananothersquaremarkedB.Finally,yourteacheraddedblackrectanglestothesecondimageanditbecameapparentthatsquaresAandBhadactuallyidenCcaldarkness.Theseimagessucceededinfoolingyourbrain.Theywereillusions.Youobservedarealphenomenon.Whatyousawdependedonchangesinthelight.Aphenomenonisaneventthathappensintherealworldandthatoccursoverandoveragain.SomeCmesyoucanobservethingsthatappearverystrangebutareactuallyreal.Forexample,haveyoueverseenthemoondisappearinthemiddleofthenighteventhoughitisabovethehorizonandtherearenocloudsinthesky?HoldtheCpsofyourthumbandindexfingernexttoeachothersothattheyarejustabouttouching.Holdthemupsothattheyarenexttoyoureyeandlookbetweenthematabrightwhitebackground.Youshouldjustbarelyfeelyourthumbtouchingyourfinger.Youshouldseeoneormoresmallblacklinesbetweenyourfingers.Fromwheredidtheselinescome?Thisisarealthingyouareseeing,notanillusion.Yourbrainisnotgeenganythingwrong.Thisgoalinthisunitistofigureoutwhathappenstomakepeopleseethings,whethertheyarerealorillusions.InvesCgaCngphenomenawillhelpyoulearnhowlightaffectswhatyousee.Inscienceclass,youwillobservedifferentphenomenaalmosteveryday.Bytheendoftheunit,youmaybeabletoexplainhowyoucouldseethetwoimagesfromclass.ObservingtheTwoIllusionsinClassAnimportantpartofscienceismakingobservaCons.AnobservaConistheactofpayingcarefulaPenContoeventsthathappenintheworld.Thisiswhatyoudidinclass.YoupaidcloseaPenContowhatyoucouldseewhenyoulookedatthetwoimages.MakinggoodobservaCons,pluslearningthesciencethatgoeswiththem,willhelpyoutoexplainthingsthathappenaroundyou.WhatQuesAonsDoYouHave?ListquesConsyouhaveaboutlight,seeing,oraboutthetwoimagesfromclassnowthatyouhavefinishedreading.

WhyIsLightImportant?Youalreadyknowthatlighthelpsyousee.Butdidyouknowthatifyouunderstandthebehavioroflight,youcanalsounderstandhowcellphonesandmicrowaveovenswork?ThescienCficideasthatexplainthebehavioroflightalsoexplainhowcomputers,televisions,satellites,GPS,andmanyothersystemswork.Infact,manyscienCficdiscoveriesfromthelast100yearsarebasedonthesameprinciplesthatexplainthebehavioroflight.Youwillnotstudyalloftheseinclass,butyouwilllearnaboutmanyofthem.YoumightalsodecidetoinvesCgateotherusesoflightonyourown.Youmaybesurprisedtolearnthatlightplaysanimportantroleinjustabouteverythingaroundyou.

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Lesson3–WhatDoWeNeedtoSeeanObject?Lesson3.1–Probingideas:Seeingobjectsaroundtheroom.

Whatwasthepointofthelastlesson?

Whatwillwedo?Wewillexploresomeofthethingshumansneedinordertosee.Wewilltrytoex-plainwhywecanseesomeobjectsbutnotothers.

ProcedureLookattheimageyourteacherprojects.Whycanthegirlseethetree?

Lookattheimageyourteacherprojects.Whydoesn’tthegirlseethecar?

Asyourteachernamesobjectsintheroom,recordtheminthedatatable.Thenputacheckmark(✓)intheappropriatecolumn.Youwillnotbeabletoseeeverythingyourteachernames.ItisimportantthatyoukeepyourbodyandyoureyesinthesameposiConasyoucollectdata.

Objects around the Classroom I Can See I Cannot See

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Conclusion

1. Whatfactorsaffectwhetheryoucanseeanobjectornot?

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Lesson3.2–DeterminingthecondiAonsforsight-thelightbox.


Whatwillwedo?Wewillgatherevidenceaboutwhatneedstohappeninorderforpeopletoseeanobject.

ProcedureFollowyourteacher’sdirecCons.RecordyourobservaConsfromeachstepbeforeyoumoveontothenextstep.

Lookintothelightbox.Besurethelidandtheflapremainclosed.Inthedatatable,drawwhatyousee.Keepthelightboxlidclosed.Openthesideflap.Lookintothelightbox.Inthetable,drawwhatyousee.

Data

Conclusion

1. CompareyourobservaCons.

2. WhywereyourobservaConsdifferent?

Observations

Lid and Flap Closed Lid Closed and Flap Open

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Yourteacherwilladdadividertoyourlightbox.Keeptheboxlidclosedandthesideflapopen.Drawwhatyouseeinthefollowingspace.Includeasmuchdetailasyoucan.

Conclusion1. Compareyourdrawingwithotherstudents’drawings.Howcanyouexplainthedifferences?

2. ListthecondiConsthatneedtobemetinorderforpeopletoseeanobject.Thislistshouldbe

agreeduponbythewholeclass.

3. Imaginethatyoulookoutthedoorofyourscienceclassjustasafriendwalksbyandwavestoyou.Explainhowyoucanseeyourfriendinthehall.BesuretouseallofthecondiConsyoupreviouslylistedinyourexplanaCon.

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Reading3.3–PictureThis!

Ge`ngReadyLookcloselyatthepicture.Holdthepaperclosetoyourface.Now,setyourbookdownandlookatthepicturefromacrosstheroom.Whydothesmallpicturesyoucanseeupcloselooklikeonebigpicturefromacrosstheroom?

Inthisreading,youwilllearnhowasimilarideamakesthepicturesthatyouseeonTV.HowDoPeopleSeeObjectsaroundThem?Inclass,youlearnedaboutthingsthataffectwhatpeoplesee.Youlearnedthatthegirlintheimageyourteacherprojectedcanseethetreebecauselighttravelsfromthesun,bouncesoffthetree,andentershereye.

Inthesecondimageyourteacherprojected,somethingdifferenthappens.Lightfromthesunbouncesoffthecar,butthisCmethegirlcannotseethecar.Someofthelighttravelstowardher,butitcannotenterhereye,becausethewallblocksitspath.Ifthelightbouncingoffthecardoesnotenterhereye,thegirlcannotseethecar.DoyouthinkthegirlinImage1canseethesun?Why?(Besuretowriteaboutthepaththelightmighttake.)

DoyouthinkthegirlinImage2canseethesun?Explainyourideas.(Besuretowriteaboutthepaththelightmighttake.)

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InLesson2,youlookedforobjectsaroundtheroom.Youlearnedthatyoucouldonlyseesomeoftheobjectsfromyourseat.Youcouldnotseeotherobjects,eventhoughsomeofyourclassmatescouldseethem.YoualsolookedintotheendofalightboxandlearnedthatsomeCmesyoucouldseewhatwasinside,andsomeCmesyoucouldnot.YourclassusedtheseacCviCestodevelopalistofcondiConsthatneedtobemetinorderforhumanstoseeanobject.Asyouread,thinkaboutthesecondiConsandhowtheyaffectwhatyouseeonatelevision.ADifferentExperiencewithSeeing:HowDoISeeObjectsonTelevision?Ifyouhaveatelevisioninyourhome,turniton.Whatdoyouseeonthescreen?Youprobablyseeaperson,someobjects,orasceneindoorsoroutdoors.However,thereisadifferencebetweenseeingtheactualobjectandseeingtheobjectontelevision.Toseetheobject—likeachair—inreallife,youneedasourcetoprovidelight,andyouneedthelighttobounceoffthechairtoyoureye.Toseeachairontelevision,youdonotneedanaddiConalsourceoflighttobounceoffofthechair.Thetelevisionisthelightsource.Thetelevisionproduceslightthatgoesdirectlytoyoureyes.AnimageontelevisionisbothanobjectandalightsourceatthesameCme.Thatiswhyyoucanseeobjectsontelevisioneveninaroomwithnolights.LookatyouracCvitysheetfromAcCvity2.2toreviewyourlistofcondiConspeopleneedtosee.Explainwhatisdifferentaboutseeinganobjectinaroomandseeinganimageontelevision.UsethelistofcondiConsinyourexplanaCon.

Thedifferencebetweenseeinganobjectandanimageontelevisionisthatanobjectmusthavealightsourcethatisbouncinglightoffofitforustoseeit.Whenweseeanimageonthetelevision,theimageisboththeobjectandthelightsource.Pointouttostudentsthatthistrueforanylightsource;thistrueforanylightsource.Ifyoulookatalightbulb,itisboththeobjectandthelightsource.HowIsanImageonTelevisionSimilartothePictureattheBeginningofThisReading?Whenyouseeobjectsontelevision,youarereallyseeingmanyCnydots.Together,thedotscreateanimagethatlookslikesomethingreal.Thesedotsarecalledpixels.Onsometelevisions,especiallyoldones,youmaybeabletoseethepixelsifyoulookatthescreenclosely.Evenifyoucanseethepixelsupclose,theyaretoosmalltobeseenasindividualdotswhenyoustandfaraway.Instead,yourbrainwillputthemtogethertomakeanimage.ThisisthesamewaythatthepictureintheGeengReadysecConworks.Ifyoustandfarenoughaway,theCnypictureslooklikepixels,andyourbrainputsthemtogethertomakealargerimage.AnExampleofPixelsWhenyouseeanimageonyourtelevisionoronamoviescreen,youareactuallyseeingmillionsofCnydotsthatalltogetherlookliketheobjectorperson.Yourbrainputsthedotstogethersothatyouseeasingleimage.YourtelevisionscreenisacollecConofCnydotsthatjointogethertomakethebigpictureyousee.EachliPledotactslikealightsourceandanobject.Thelightmovesalongastraightpathtoyoureyes.YourbraindoesnotseeabunchofliPleobjects,becauseitputsthemtogethertoseetheimageonthetelevision.

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TwoMoreExamples:NewspapersandArtworkDotpaPernsarenotonlyusedfortelevisionimages.DotsarealsousedincomputerandnewspaperimagesandinpainCngs.Ifyouhaveanewspaperathome,lookatitveryclosely.Ifyouhaveamagnifyingglass,useittolookatthenewspaperupclose.CanyouseetheCnydotsthatmakeupthepicturesandthewords?WhatdoyounoCceinthephotoofaflowerandinthecloseupofthephotonexttoit?

Manythingsintheworldtodayusepixelstomakeimages.Longago,arCstsinFrancepaintedinastylecalledpoinCllism.ImagesusingpoinCllismarecreatedbypainCngmanyCnydotsorpoints.Thecolorsofthepaintarenotmixedtogetherusingabrush.Instead,thedifferentcoloreddotsareplacedveryclosetogether.WhenyoulookatthepainCngfromfaraway,thelightfromtheroombouncesoffthedotsonthepainCngandthenentersyoureye.Yourbrainblendsthedotstogethertoformalargerimage.ComparethedotsusedinpoinCllismwiththedotscreatedonatelevisionscreen.Besurethatyourcomparisondescribeswhatisalikeandwhatisdifferent.

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Lesson4–ConstrucAngModelsofHowPeopleSeeLesson4.1–PreparingtoDevelopModels


Whatwillwedo?Wewillconstructphysicalmodelsofhowpeoplesee.OurmodelswillrepresentthekeycomponentsandrelaConshipsthatwehavelearnedsofar.

PartA:EvaluaAngaModel

Amodelcanbegoodornot-so-good,dependingonwhatitisbeingusedfor.Whenyouuseamodeltoexplainanideatosomeone,thebestmodelisusuallyasimpleone.AgoodmodelforexplainingsomethingincludesallthekeycomponentsandtherelaConshipsbetweenthem.Itisimportantthatamodelonlyincludesthosethingsandnotextrapartsthatdonothelpexplainsomething.Itisalsoimportantthatyourmodelisaccurate.YoushouldlookcarefullyatyourmodeltobesureyouhaverepresentedthecomponentsandtherelaConshipscorrectly.Yourteachershowedyouamodeloflightusingaclaylightbulbandsometoycars.1. Howcanyouusethismodeltoexplainhowpeoplesee?

2. Howcouldyouimprovethismodeloflight?ThinkaboutthecomponentsandtherelaConshipsbetweenthem.Foreachpartofthemodel,askyourselfifyoucouldexplainhowpeopleseewithoutconsideringthatcomponent.Alsoaskyourselfifthereissomepartofseeingthatyourmodeldoesnotrepresent.

PartB:PlanYourModel

3. Amodelneedstobeconsistentwithalltheevidence.InLesson2,yougatheredevidencethatamodelofseeingneedstoincludefourkeycomponents:alightsource,anobject,aneye,andpathsbetweenthelight,theobject,andtheeye.Lookatthesuppliesyourteacherhasprovided.Whatwillyouusetorepresenteachoftheseparts?

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PartC:BuildandEvaluateYourModel4. Nomodelisperfect.Everymodelhasstrengthsandweaknesses.Whatarethestrengthsand

weaknessesofyourmodel?

5. Whatdidyoulearnasyoumadeyourmodelofhowpeopleseeanobject?

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Reading4.2–Modeling

WhyDoScienAstsUseModels?Whenyouhearthewordmodel,youmightthinkoffashionmodelsormodelairplanesormodelcars.ScienCstsusethewordmodelinaspecialway.Inscience,amodelisawaytorepresentanidea,process,orsysteminordertodescribe,explain,orpredictsomething.Modelshelptoexplainthingsthataredifficulttounderstandordifficulttoobserve.Forinstance,youcannotseeyourheart,butyoucanuseamodelofahearttoexplainhowitpumpsbloodthroughyourbody.Modelscanalsorepresentthingsthataretoobigortoosmalltoobserve.PeoplecannotobservethewholeEarthatonce,buttheycanusemapsandglobesasmodelstohelpthemexplainphenomena.Peopleontelevisionusemapstohelpthemexplainweatherorearthquakes.GlobescanhelpexplainwhyitisdayandnightatdifferentCmesindifferentpartsoftheworld.Inclass,youhavebeendevelopingamodelofhowlightmakesitpossibleforpeopletoseeobjects.Yourmodelhelpsyouunderstand,anditcanalsohelpyouexplainittootherpeople.ScienCstsusemodelstocommunicate.Asyoulearnmoreaboutlight,youmightdecidethatyouneedadifferentmodelthantheoneyoumadetoday.ScienCstsrevisetheirmodelsastheylearnnewthings.ItisOKifyourmodelofhowpeopleseegetsrevised,too.ModelshelpscienCststhinkaboutpossibleanswerstotheirquesConsaboutphenomena.YouwilluseyourmodelofseeingtoexplainhowyoucouldseethestrangeimagesinLesson1.IsItOKthatMyFriend’sModelIsDifferentfromMine?Youandyourclassmatesmayhaveconstructeddifferentmodelsofhowpeoplesee.DifferentmodelscanbehelpfulbecausetheymayshowdifferentinformaConaboutthesamephenomenon.Allmodelshaveadvantagesanddisadvantages.EvengoodmodelscanolenbemadebePer.Youwillbelearninghowtoevaluatemodelstodecidewhatisgoodandwhatneedstobechanged.ScienCstsevaluatetheirownmodelsandrevisethemwhennecessary.Forexample,newdatamakescienCststhinkaboutaphenomenoninanewway.Dataisawordyouwilluseoverandoveragaininscience.WhenscienCstsmakeobservaCons,theytakecarefulnoteswhiletheyareobservingsomethingwiththeirsensesormeasuringitwithinstruments.Thenotestheywriteorrecordarecalleddata.Whentheyusedatatosupportanidea,theyareusingthedataasevidence.Youwilldothesamethinginscienceclass.YourdatamaycomefromyourownobservaConsandmeasurements,oritmaycomefromatableorgraphthatsomeoneelsemade.Whenyouusedatatoexplainanidea,youareusingthedataasevidence.WhenscienCsts—oryou—developamodel,themodelneedstobeconsistentwithalltherelevantevidence.AnExampleofScienAstsRevisingTheirModelsScienCstsreviseamodelwhenitdoesnotworkverywellforexplainingsomething.Forexample,youprobablyknowthatsailorsonceexploredtheworldbysailingacrossoceans.Theydrewmapsoftheoceansandlandtoshowwhattheworldlookedlike.Thesedrawingsweresimilartotheflatmapsweusetoday.Mapsareonekindofmodelthatisdrawn.AflatmodelhelpedearlyscienCstsunderstandmostthingsabouttheworldaroundthem.However,aspeoplemadeobservaConsandtriedtoanswernewquesCons,theyfoundthataflatmodelofEarthdidnotworkforeverything.Forexample,sailorscouldseethetopsofmastsasshipsapproachedthemoverthehorizon.IfEarthwasflat,thatwouldnotmakesense.Theywouldnotseethetopsofmastsfirstandthengraduallyseetherestoftheship.TheyalsowonderedwhythesunchangesitsposiConintheskythroughouttheyear.AflatmodelofEarthwasnotconsistentwiththedatatheyobserved.

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ScienCstsbegantoconsideranewmodel.TheybegantousearoundmodelofEarth—likeaball.AroundEarthmodelcanexplainwhythetopsofships’mastsarevisiblefirst.AglobemodelcanexplaintheposiConsofthesuninthesky,anditcanexplainseasons.Later,photographstakenfromspaceshowedtheshapeofEarth.BeforescienCstsknewforsure,theyhadtokeeptesCngtheirmodeltoseewhetheritworkedtoexplaintheirobservaCons.Today,aglobeservesasagoodmodelformanythingsscienCstswanttoexplain.Aflatmapisgoodforshowinghowtogetfromoneplacetoanother.However,itisnotgoodforexplaininghowthesunrisesandsetsorhowashipcansailaroundtheworld.Everymodelhasadvantagesanddisadvantages.Amodelthatexplainswhatyouknowtodayabouthowlighthelpspeopleseemightnotbeagoodmodelforwhatyouwilltrytoexplainlaterintheunit.Youmightreviseyourmodelasyougathermoredata.ScienCstsrevisetheirmodels,andyoucanreviseyours,too.CheckYourUnderstandingGobacktothestatementsintheGeengReadysecCon.Nowthatyouhavefinishedreading,usethecolumnontherighttocheckwhetheryouagreeordisagreewitheachstatement.

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Lesson4.3–BuildingtheConsensusModel

Whatwasthepointofthelastlesson?Wewillcombinethepartsofourmodelsthatweagreeaboutintoonemodelcalledaconsensusmodel.Theconsensusmodelwillbeadiagraminsteadofaphysicalmodel.

Whatwillwedo?Wewillcombinethepartsofourmodelsthatweagreeaboutintoonemodelcalledaconsensusmodel.Theconsensusmodelwillbeadiagraminsteadofaphysicalmodel.

QuesAons:

1. Modelshaveadvantagesandtheyhavedisadvantages.Whatdidyouthinkwerethebestpartsofotherstudents’models?Why?

2. Howdoesyourdrawnmodelcomparewiththeconsensusmodelyourclasscreated?Describewhatissimilarandwhatisdifferentaboutthem.

3. Useyourclassconsensusmodeltoexplainwhyyoucannotseeyourgrandmaintheotherroom.

4. WhatdoyousCllneedtoknowabouthowlighthelpsyousee?WhatdoyousCllwanttoknowabouthowlighthelpsyousee?

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Reading4.4–FasterthanaSpeedingBullet

Ge`ngReadyInthisreading,youwilllearnabouthowfastlightmoves.Beforeyouread,thinkofsomeofthefastestthingsyouhaveheardabout.Fillinthechartwithyourideas.

Whenpeoplesaythatturningonalightswitchlightsuptheroom,whatdotheymean?Inclass,youconstructedamodelthatshowswhatisneededforpeopletoseeobjectsinaroom.Thekeycomponentsinyourmodelwereanobject,aneye,alightsource,andthekeyrelaConshipbetweenthesewasthestraightpathsbetweenthem.Whenyouturnonalightbulb,lighttravelsfromthebulboutwardinalldirecConsandhitsobjectsintheroom.Youseetheobjectsbecauselighttravelsfromthelightbulb,bouncesofftheobjects,andthenentersyoureye.Iflighthastotravelbackandforthacrosstheroombeforeyoucanseeanobject,whydoyouseethingsinaroomassoonasyouturnonalightswitch?Theanswerhastodowiththespeedoflight.Lightisveryfast.YouwillreadabouthowscienCstsfiguredouthowfastlightis.HowDoScienAstsMeasureHowFastLightMoves?Youdonothavetowaittoseethingsaleryouturnonalight,becauselightmovessofast.YoudonotevennoCcelightmoving.Itprobablyseemslikelightgetsfromabulbtoanobjectandbacktoyoureyeinstantly.Iflightmovessofast,howcanscienCstsmeasureit?AfamousscienCst,Galileo,triedtomeasurehowfastlightmoves.Galileowantedtomeasurethespeedoflightintheearly1600s.Todothis,hesentanassistanttothetopofahillwithalamp.HewantedtomeasurehowmuchCmeittookforlighttotravelfromonehilltoptoanother.TheassistantrecordedwhatCmeitwasonhiswatchasheturnedonhislight.Galileo,standingonanotherhill,turnedonhislightimmediatelyalerhesawhisassistant’slight.TheassistantthenrecordedtheCmeattheinstanthesawGalileo’slight.Galileo’sideawasthattheassistantwouldhavemeasuredtheCmeittooklighttotravelfromonehilltotheotherandthenbackagain.However,thisdidnotwork.TheCmeittookGalileototurnonhislightwasactuallymuchlongerthantheCmeittookthelighttotravelfromonehilltothenext.WhenGalileofirsttriedtomeasurethespeedoflight,heandhisassistantstoodonhilltopswithlamps.Whywasitnecessaryforthemtobestandingonthetopofhillstoconducttheirexperiment?(ThinkaboutthefourcondiConsneededtoseeanobject.)

Moving Object How Fast does it go?

Fastest human runner

Fastest bicycle rider

Fastest animal

Fastest Car

Fastest man-made object

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Usingtheconsensusmodelyouandyourclassmatesconstructedinclass,explainhowGalileocouldseehisassistant’slight.ThiscanbedonebyshowinghowthekeycomponentsinthemodelrepresentwhatwasinvolvedinGalileoseeinghisassistant’slight.

WhatDoWeKnowabouttheSpeedofLightToday?Inhisexperiment,Galileoandhisassistantwereseveralmilesapart.Today,humanscansendobjectsmuchfartheraway.In1969,theUnitedStatessentastronautstothemoon.Themoonisabout240,000miles(365,000km)awayfromEarth.ThisisliketravelingaroundthewholeEarth10Cmes.Thinkabouthowlongitwouldtakeyoutodrivearoundtheearthinacar.Duringthemissiontothemoon,scienCstsnoCcedthatittookaboutonesecondforlightfromEarthtoreachtheastronautsonthemoon.LightcantravelaroundEarth10Cmesinjustonesecond.Nothingelsecantravelthatfast.Thesunismuchfartherawaythanthemoon.Travelingtothesunwouldbeliketaking37,000tripsaroundEarth.EventhoughEarthisahugedistancefromthesun,itonlytakeslightfromthesunabouteightminutestogettoEarth.Thismeansthatwhenyouseethesun,youareseeinghowitlookedeightminutesago.HowDoestheSpeedofLightComparetoOtherFastThings?Inthebeginningofthisreading,youthoughtaboutsomefastthings.Theworld’sfastestpeoplecanrunatabout25milesperhour.Acheetahcanrun70milesperhour.Thefastestanimalistheperegrinefalcon.Itcanflyover200milesperhour.Humanshavemademachinesthatcanmoveextremelyfast.Thefastestapersonhasevermadeabicyclegois167milesperhour.AThrustSSC,theworld’sfastestcar,cango760milesperhour.Thefastesthuman-madeobjectstravelinspace.AspacecralcalledtheHeliostraveledat150,000milesperhour(or241,400kmperhour).Atthisspeed,itwouldtakeaboutamonthtotravelfromEarthtothesun.Itonlytakeslighteightminutestotravelfromthesuntotheearthbecauselightmovesmuchfasterthananythinghumanshaveevermade.Lightmovesthroughspaceat670,000,000milesperhour.Thismeansthatitwouldtakeajetairplane25daystotravelthesamedistancethatlightcantravelinonesecond.Whenyoufliponalightswitch,itseemsthatlighthitsyoureyeinstantlybecauselightmovessofast.ItmovesbackandforthacrosstheroomsofastthatyoudonotevennoCceitmoving.HowCantheSpeedofLightHelpPeopleMoveFaster?OnewaythatthespeedoflightmaPerstoscienCstsiswhentheythinkaboutspacetravel.Rightnow,ifpeoplecouldtraveltoMarswiththespaceshuPle,itwouldtakeninemonthstogettoMars.ItwouldtakeanotherninemonthstogetbacktoEarth.ScienCstsatNASAarestudyinghowtousenewspaceshipscalledsolarsails.Thisisaphotoofasolarsail.TheseshipscouldtravelthousandsofCmesfasterthanthespaceshuPle.ThespaceshuPleispushedbyburningrocketfuel,butsolarsailsarepushedbylight.Thatmeanstheywouldbemuchfaster.ExperimenCngwithsolarsailsisoneofthewaysthatscienCstsusetheirunderstandingoflighttocreatesomethingnew.Asyouhavelearned,lightmovesextremelyfast,anditwillbeabletohelppeopledothingsevenfaster.InLesson4,youwilllearnaboutwhathappenstothelightthatentersyoureye.

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Lesson5–TheEyeasaLightSensorLesson5.1–HowtheEyeWorks


Whatwillwedo?Wewilllearnabouthowoureyesactlikealightsensor.

ProcedureYourteacherwillprojectarepresentaConoftheeye.Usethefollowingspacetodraworwritenotesaboutwhatyourteacherreviewsinclass.

Youaregoingtogoonahuntusingalightsensor.Thesensoronlydetectslightthatcomesfromobjectsdirectlyinfrontofit.Thelighthastobounceofftheobjectorcomefromalightsourceandtravelstraightintothesensor.Inthedrawings,whereisthelightthatthelightsensordetectscomingfrom?Explain.DrawlinesandarrowsinthedrawingstoshowthepaththelighttravelsunClitentersthelightsensor.

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Usethelightsensortomeasurelightindifferentplacesintheroom.RecordthelocaCon,themeasurement,andtheunitsinthefollowingtable.

Wherearethebrightestpartsoftheroom?Whatrangeofvaluesisshownonthedatalogger?

Wherearetheleastbrightpartsoftheroom?Whatrangeofvaluesisshownonthedatalogger?

Conclusion

1. Likethelightsensor,theeyeactsasasensoroflight.Lighthastocomeintothelightsensorandintoyoureyefromoutside.Howdoestheconsensusmodeloflighthelptoexplainwhichpartsoftheroomarethebrightest(ortheleastbright)totheeyes?

2. Ifnolightiscomingfromanyobjectintoyoureye,thenwhatwillyousee?WhatevidencefromaclassroomacCvitysupportsyouranswer?

Location Light Measurement

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3. Doesalightsensordetectanobject,ordoesitdetectthelightcomingfromanobject?Howdoesthiscomparewithhowtheeyeworks?

4. WhydoesitmakeadifferenceinwhichdirecConyoupointthelightsensor?

5. WhydoesitmakeadifferencehowfarawaythelightsensorisfromtheobjectatwhichitispoinCng?

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Lesson5.2–ExploringShadows


Whatwillwedo?Wewillexploreshadowsinourworld.

ProcedureIfitisasunnyday,gooutsideandlookforashadow.Inthefollowingspace,drawwherethelightsourceiscomparedtotheshadowandtheobjectthatmadetheshadow.Ifpossible,observetheshadowagainanhourlater.Comparethesize,shape,andposiConofthetwoshadows.YoucouldalsodothisacCvityusingashadowinside.

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Reading5.3–EyesintheAnimalKingdom

Ge`ngReadyTrythisathome.Gointoasmallroomwithamirror,likeabathroom.Lookcloselyinthemirroratyoureyes;thenturnoffthelightandmaketheroomasdarkaspossible.Ifyoucannotmaketheroomdark,shutyoureyesandcoverthemwithyourhands.Waitforseveralseconds,andthenturnthelightsonasyouconCnuetolookatyoureyesinthemirror.WhatchangesdoyounoCceinyoureyesimmediatelyaleryouturnthelighton?Whydoyouthinkthischangehappens?

Doyouthinkthesamechangehappenstoanimals’eyes?Inthisreading,youwilllearnwhyyoureyeslookdifferentdependingonwhetherthelightsareonoroff.Youwillalsolearnwhetheranimals’eyesdosomethingsimilarordifferent.HowDoMyEyesSenseLight?Inclass,youlearnedhowthehumaneyeworksasalightsensor.Whenyouseeanobjectinaroom,thelightisbouncingoffofthatobjectandgoingstraightintoyoureye.Howdoesyoureyehelpyousee?Theeyehasseveralimportantparts.Theopeninginthecenteriscalledthepupil.Inthepicture,thepupilislabeled.Itlooksblack,butitisreallyjustlikeaclearwindowthatletslightintotheeye.ThecorneaisaprotecCvecoveringoverthewholeeye.Itkeepstheeyefromgeengscratched.Thelensintheeyeislikethelensineyeglassesorinacamera.Thelensfocusesthelightcomingintotheeye.ThelensfocuseslightontothebackoftheeyeballonanareacalledthereCna.SensorsinthereCnadetectthelightthatreachesthem.ThosesensorssendasignaltothebrainthroughtheopCcnerve.HowDothePartsoftheEyeWorkTogether?Whenyouseealightbulb,severalthingshappen.First,someofthelightcomingfromthebulbentersyoureyeandreachesyourreCna.Second,yourreCnasendsasignaltoyourbrain.Third,yourbrainrecognizesthatthesignalisalightfromalightbulb.Lookatthediagram.Ifacoffeemugwereintheroomsothatyoucouldseeit,thensomeofthelightfromthelightbulbwouldbebouncingoffofthemug.SomeofthelightbouncingoffofthemugwouldenteryoureyeandreachthereCna.Asignalwouldgotoyourbrain,andrecognizeitastheimageofamug.Alothastohappenforyoutoseesomething;butithappensveryquickly.

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UsingEquipmentasaLightSensorYoureyeisasensor.Specialequipmentalsocanactasasensor.Thelightsensorsthatyouusedinthislessonareoneexample.Whenyoupointedthesensoratanobject,itdetectedthelightcomingfromthatobject.Justlikewithyoureyesorwithcameras,lighthadtoenterthesensorinordertobedetected.Insteadofsendingasignalthatyourbrainrecognizesasanimage,thelightsensorsendsasignaltoasmallcomputer.Thiscomputerreceivesthesignalanddisplaysanumberthattellshowmuchlightisenteringthesensor.Whenyousawanobjectintheroomthatlookedbrighttoyoureyes,thelightsensorshowedaveryhighnumberonitsdisplay.YoumayhavegoPenahighnumberwhenyoupointedthesensoratthelightsoratawindow.Whenyousawanobjectthatlookeddimtoyoureyes,thesensorshowedalownumberonitsdisplay.YoumayhavegoPenlownumberswhenyoupointedthesensorundertablesordesks.Whenlightentersasensor,acomputergivesinformaCon.Whenlightentersyoureye,yourbraingivesyouinformaCon.DoAnimalEyesWorklikeHumanEyes?Justlikehumaneyes,animals’eyesworkbydetecCnglight.However,therearesomedifferencesbetweenhumaneyesandsomeanimals’eyes.Inthisreading,youwilllearnaboutthreeanimalsthathaveeyeswithspecialcharacterisCcs.PolarBears

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Haveyoueverplayedoutsideinthesnowonasunnydayorplayedonawhitesandbeachonasunnyday?Ifyouhave,youknowhowbrightitiswhenthesun’slightbouncesoffofthewhitesnoworthewhitesand.YoualsomayhavenoCcedthatitisdifficulttoseeinbrightlightwithoutsquinCng.Whydopeoplesquint?Peoplesquintsothattheireyelidssqueezetogetherandcoverpartoftheiris.WhentheirisisparCallycovered,thepathofsomeofthelightgoingintotheeyesgetsblocked.Polarbearsliveoutsideinthesnow.Becausepolarbearshavetohuntforfoodinintensesunlight,theireyeshavetoallowthemtoseeinverybrightlight.PolarbeareyeshaveaprotecCve,clearcoverovertheireyeballs.Thebearscanseethroughthiscoveringtohunt.Thecoveringprotectstheireyesfrombrightsunlightandthelightthatbouncesoffthesnow.Itiskindoflikehavingbuilt-insunglasses.ThisprotecCvecoveralsohelpsprotectabear’seyeswhenitswimsunderwater.CatsCatsalsohaveeyesadaptedtotheirenvironment.Asnaturalhunters,catsneedtohavekeensensesinordertostalktheirprey.CatscanseealmostaswellashumansduringthedayCme,buttheirnighemevisionismuchbePer.Althoughcatscannotseeincompletedarkness,theycanseemuchbePerthanhumansinenvironmentsthatappeardarktous.Infact,catscanseesixCmesbePerthanhumansinplaceswithlowlight.Thereareseveralreasonsforthis.CatreCnasaremoresensiCvethanhumanreCnas.Duringtheday,acat’spupillookslikeaslit.Thisslitdecreasestheamountoflightenteringtheeyesandpreventsthecatfromhavingtosquint.Aroundpupil,likeinahumaneye,wouldletintoomuchlight.Atnight,orwhencatsareindarkplaces,theirpupilscanopenthreeCmeswiderthanthoseofhumans.Thewideropeningletsinmuchmorelight.Likepolarbears,theyhaveatransparentprotecCvecoverovertheireyesthatallowthemtoseewellinbrightdaylight.Youmayhaveseenacat’seyesappeartoglowinthedarkwhenlightisshinedonthem,asinthephoto.Thetransparentcovercausescats’eyestoappeartoglowatnight.YoumayhavealsonoCcedthisondogs.GiantSeaSquidThisisaphotoofasquid.Giantseasquidsareknowntohavethelargesteyesofanyanimalintheanimalkingdom.Eventhoughmanyanimalsarelargerthantheseasquid,nonehavesuchbigeyes.Somegiantseasquidshaveeyesaboutthesizeofyourhead.Theirhugeeyeshaveverylargepupilsthatletinasmuchlightaspossible.Sodeepinthesea,whereitisverydark,theireyescanletintheliPlebitoflightthatreachesthem.Evensquidsandcats,whichcanseeinverydarkplaces,needsomelighttosee.Evenwithlargepupils,ifnolightenterstheeye,thentheanimalwillnotbeabletosee.

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SummarizingAnimportantskillinanysubjectissummarizing.Whenyousummarizesomethingyouhaveread,youtellthemainideas.Thatmeansthinkingaboutwhatseemstobethemostimportantideasinwhatyouread.Inthefollowingspace,summarizewhatyouhavelearnedaboutanimaleyesintoday’sreading.(Thinkaboutwheretheyliveandwhattheireyeseyesneedtobeabletodofortheanimaltosurviveinitsenvironment.)ThebeginningofasummaryiswriPenforyoutogetyoustarted.Differentanimals’eyesworkindifferentways.Howtheireyesworkdependsonthefollowingfactors:

Showyourunderstandingbyfillingintheblanksinthefollowingsentences.Inbrightlights,thepupilsofahuman’seyes_____________________.Indarkness,thepupilsofahuman’seyes________________________.

Explainwhythefollowingsentenceisnotcorrect:Becausecatshavesuchgoodeyes,theycanseewhenitiscompletelydark.

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Lesson6–HowAreShadowsCreated?Lesson6.1–IntroducingShadows


Whatwillwedo?WewillexploreshadowsanduseourlightmodeltoexplainourobservaCons.

ProcedureTheteacherwilldimthelightsintheclassroom.Putapieceofwhitepaperonyourdesk.Useyourhand(oranobject)andaflashlighttocreateashadowonthepaper.ExplorewhathappenstotheshadowinthreecondiCons:

movingthehandorobjectmovingtheflashlightmovingthepaper

RecordyourobservaConsinthedatatable.DiscussthefollowingquesConswithyourgroup:Howdoestheshapeoftheshadowcomparetotheshapeoftheobject?Howcanyouchangethesizeoftheshadow?HowcanyouchangethelocaConoftheshadow?

Data

Conclusion

1. Whatpartsofthelightmodeldoyouneedtoexplainhowyouseeashadow?

Conditions Observation

Moving the Object

Moving the Flashlight

Moving the Paper

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2. Howdoesthelightmodelhelpyouexplainthattheshapeoftheshadowisliketheshapeoftheobject?

3. HowdoesthelightmodelhelpyouexplainhowyoucanchangethelocaConoftheshadow?

4. Howdoesseeinganobjectcomparewithseeingashadow?

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Reading6.2–AMidnightCrime

Ge`ngReadyReadastoryaboutacrimethattookplaceonadarknight.WewillusewhatwehavelearnedaboutlightandshadowstoanswerquesConsandsolvethecrime.AMidnightCrimeHalloweenwasperfect,withaclearanddarksky.ManypeoplecametotheSmiths’Halloweenparty.EveryonehadagreatCme,andsomepeoplestayedunCldawn.Alereveryonelel,theSmithsdiscoveredthatsomeexpensivejewelrywasmissing.Theycalledthepolice.ThepoliceaskedeveryonewhohadbeenatthepartytoanswerafewquesCons.Apoliceofficerlistenedcarefullytoeachperson’sstory.Mr.Jonessaid,“IleltheSmiths’partyaroundmidnight,andIwalkedtomycar.Itwascold,buttheskywasclearwithnoclouds.Itwastotallydarkoutside.WhenIgotinmycartoleave,Isawsomeonewalkingoutofthehouseholdingadecoratedwoodenbox.Iturnedonthecarlights,andthepersonimmediatelyturnedaroundandwalkedawayfromme.Heorshewalkeddirectlytowardthewallnexttothehouse.IcouldseetheshadowonthewallgeenglargerandlargerunClthepersondisappearedaroundthecorner.AtthatCme,Ididnotsuspectanything,soIjustdroveaway.”Thepoliceofficerthoughtforaminuteandsaid,“YouareunderarrestonsuspicionofstealingtheSmiths’jewelry.Yourstatementincludestoomanyimpossibledetails.IsuspectyouknowsomethingaboutthedisappearanceofthejewelrycollecCon.”FollowUpQuesAons1. WhataretheimpossibledetailsinMr.Jones’sstatementtothepolice?Explainwhythesedetails

areimpossible.

2. ConstructadrawnmodelthathelpsexplainhowMr.Joneswouldhavereallyseenaperson’sshadow.

Detail in the Statement Why is That Impossible?

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3. IfMr.Joneshadnotturnedonhiscarlights,wouldhehavebeenabletoseetheperson?Wouldhehavebeenabletoseetheperson’sshadow?Explain.

4. Explainwhylightisnecessarytoseeanobject.

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Lesson6.3–ConnecAngShadowstotheLightModel


Whatwillwedo?Wewillusethelightmodeltoexplainhowshadowsarecreatedandhowweseeshadows.

ProcedureLookatthediagram.Thediagramshowstheconsensusmodelwithanewcomponentadded.Behindtheobject(thetriangle)isasurface.Thesurfacecouldbeapieceofpaper,awall,orthetopofyourdesk.Thetrianglerepresentsanyobjectthatcouldmakeashadowonthesurface.Constructadrawnmodelofhowshadowsarecreatedandhowyouseeshadows.

Drawtheshadowoftheobjectonthescreen.Addlinesandarrowstoyourdrawingtoshowhowtheshadowiscreatedandhowtheeyeseestheshadow.MakesureyourdrawingincludesallthecomponentsofthelightmodelthatrepresentthecondiConsnecessarytoseeanobject.

Conclusion

1. DescribeyourmodelinafewsentencessothatyoucouldpresentyourexplanaContotheclass.

2. UseyourmodeltoanswerthefollowingquesCons.

a. Whatissimilarbetweenseeinganobjectandseeingashadow?

b. Whatisdifferentbetweenseeinganobjectandseeingashadow?

c. Modelscanbeusefulnotonlytounderstandandexplainbutalsotopredictsomethingbeforeexperiencingit.Usingyourmodel,predictwhatalightdetectorwoulddetectwhenpoinCngtowardtheshadowedareaonthescreen.Explain.

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Reading6.4–AllShadowsAreNottheSame

Ge`ngReadyHaveyoueverbeenoutsideonasunnydayandwatchedyourshadow?Maybeyoudancedinfrontofawalltowatchhowyourshadowmoves.Maybeyouwatchedyourshadowchangeasyougotclosertoabuilding.Inthisreading,youaregoingtodoafewsimpleacCviCestolearnmoreaboutshadows.Allyouwillneedislightandyourownhand.AsyoudotheacCviCes,trytothinkaboutwhatishappeningandwhy.Youmightbeabletofigureoutsomethingsevenbeforeyoureadaboutthem.TryThisatHomeGointoaroomwithalotoflightsandwindows.Turnonallthelights,andholdyourhandaboutsixinchesaboveatableorthefloor.Trythisduringthedayifyoucan.Lookattheedgesofyourhand’sshadow.Aretheyblurryoraretheyclearandstraight?Now,gointoaroomwithnowindowswhereyoucanturnallthelightsoffbutonelightontheceiling.Thisshouldbeasmalllight,notalongfluorescentlight.Iftheroomonlyhasadeskortablelamp,youcanuseoneofthoseinstead.Holdyourhandsixinchesabovethetableorflooragain.

Howdoesthisshadowcomparetotheshadowyoumadebeforewithlotsoflights?Makesuretodescribehowbothshadowsarethesameanddifferent,payingspecialaPenContotheedgesoftheshadows.

Whathappenstotheblurrinessoftheshadowifyoumoveyourhandcloserandfartherfromthelight?Whathappenstotheshadow’ssize?

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YouprobablynoCcedthatyourshadowwasfuzzywhenthereweremanylightson.Yourshadowwaslessblurrywhentherewasonlyonelighton.Inthisreading,youwilllearnhowthelightmodelcanhelpyouexplainwhytheedgesoftheshadowofyoursamehandlooksclearsomeCmesandblurrysomeCmes.

HowDoIMakeaClearShadow?Beforeyoulearnwhatmakesafuzzyshadow,youshouldunderstandwhysomeshadowshaveclearedges.IntheGeengReadyacCvity,yousawthatyourhandhadaclearshadowwhentherewasonlyonelighton.Inclass,youusedalightmodeltoexplainhowashadowisformedwhenasinglelightsourceshinesonanobject.Youmayhavedrawnsomethingsimilartothefollowingexample.Lightleavingalightsourcetravelsinstraightlines.Ifahandblocksthepathbetweenthelightsourceandthetable,thenashadowwillbeformedbehindthehand.Why?Lightthathitsthehandwillnotgettothetable.Lightthatmissesthehandwillgettothetable.Wheneveryplaceonthetableeitherreceiveslightordoesnotreceivelight,theshadowhasclearedges.Thereisaclearborderbetweenthelitandunlitareas(theshadow)onthetable.Lookatthepreviousdiagram.NoCcehowthediagramrepresentsthelightsource,yourhand,andtheshadowonthetable.

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HowCanIMakeaFuzzyShadow?IntheGeengReadyacCvity,younoCcedthatturningonmorethanonelightsourcecausedtheshadowofyourhandtobefuzzy.Itmighthavecausedtheshadowstolookliketheyoverlap.Youcanunderstandwhythishappensbydrawingthelightmodelwithtwolightsources.Thefollowingdrawingshowsthelightmodelwithtwolights.ItlookslikeonlyLightSource#1isshiningonthehandinthediagram.NolightiscomingfromLightSource#2inthefollowingdiagram.

IfonlyLightSource#1isturnedon,therewillbeaclearshadowonthetableorfloor.However,somethingdifferenthappenswhenyouturnonLightSource#2atthesameCme.Lookcloselyatthefollowingtoseehowtheshadowchanges.ThefollowingdiagramshowslightfromLightSource#1asdoPedlinesandlightfromLightSource#2assolidlines.

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Thisdrawingwillmakemoresenseifyouthinkabouteachpartofthedrawingandaboutwhatyoudid.ThetableisrepresentedbythelineacrosstheboPomofthedrawing,butthelightsarehiengyourhandfromdifferentdirecCons.Canyouseethatthedarkpartoftheshadowwouldbethepartinthemiddleofyourhand?Nolightfromeitherlightsourcegetsthroughyourhandtoreachthisarea.Theshadowthereisdark,butnexttoitareareasthatarelitbylightfromonlyoneofthelightsources,becauseyourhandblocksthelightfromtheotherlightsource.Theseareasarelessdark,buttheyarenotbright.Theseareasarethepartsoftheshadowthataregrayorblurry.AnotherExampleThephotoshowstheshadowformedwhentwolightsourcesshineonaballonasCck.NoCcethatthereisaverydarkpartoftheshadowwherenolightfromeitherlightsourcereachesthewall.NoCcethattherearetwolessdark(orgray)areaswherelightfromonlyonesourcereachesthewall.Whentherearetwolightsources,ashadowhasdarkerandlighterareas.Thedarkareaiswherenolightfromeithersourcereachesthewall.Theareasthatarenotasdarkareformedwherelightfromonlyonesourcereachesthewall.ComparingShadows:OneLightSourceComparedtoTwoLightSourcesShadowsareformedwhenanobjectblockslightfromreachingsomething.Youusedyourhandtoblockthepathbetweenthelightandthewallortable.ThepictureshowsaballonasCckblockingthepathbetweenthelightsandthewall.Whenthereisonlyonelightsource,thereisaclearborderbetweenthedarkareaandthelightareaonthewall.Whentherearetwolightsources,thedarkareaoftheshadowissurroundedbyareasthatarenotasdark.Theselessdarkareasmaketheedgesofshadowslookfuzzybecausetheypreventaclearborderbetweentheverydarkandvery

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lightpartsofthewall.Themorelightsourcesthereare,thefuzziertheedgesoftheshadowwilllook.WhydoyouthinkthesCckthatisholdingtheballismakingtwoshadows?Whydoyouthinkthattheyarebothgrayinsteadofdark?

Whenyouturnedonmanylightsintheroomandlookedatyourhand’sshadow,whywasthemiddlepartoftheshadowdarkandtheareasclosertotheedgelessdark?

CanaShadowBeFuzzywithOnlyOneLight?YoumayhavenoCcedthatyoucouldmaketheshadowofyourhandlookfuzzywithonlyonelightturnedon.Thiscanhappenifyourhandisclosetothelightorifthelightsourceislargeandclosetotheobject.Thelightmodelcanhelpyouunderstandwhythishappens,too.Thenextdrawingshowshowashadowisformedusingalargerlightsource.LightcomingfromthelelsideofthesourceisshownwithdoPedlines,andlightfromtherightsideofthesourceisshownwithsolidlines.Insteadofallthelightcomingfromoneplaceinthelightsource,lightcomesfromeverywhereinthelightsource.Thisisjustlikehavingseveralseparatelightsources,someatthetopandsomeattheboPom.LighterareasareformedwhenlightfromonlythetoportheboPomofthesourcecanreachthewall.Adarkareaoftheshadowappearswherenolightfromanywhereinthesourcereachesthewall.Becausethelightfromlargersourcesleavesfromdifferentplaces,theyusuallyformfuzzyshadows.

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WhenCanYouSeeShadowslikeThisinOtherPlaces?Haveyoueverseenafluorescent(floor-eh-sent)lightbulb?Theyareshapedlikelongtubes.Youmayhavethemintheceilingofyourclassroomsatschool.Shadowsformedbyfluorescentlightbulbswillalmostalwaysbefuzzybecausetheyarealargelightsource.CheckthenextCmeyouareinschoolbyholdingyourhandaboveyourdesk.YouhaveprobablynoCcedthisfuzzinessaroundshadowsbefore.Themodelthatyouhavedevelopedthroughthefirstfivelessonsallowsyoutoexplainwhythishappens.ModelsareverypowerfultoolsthatscienCstsusetohelpthemexplaintheworldaroundthem.Nowyouareusingthem,too.

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Reading6.5–StarsandtheSolarSystem

Ge`ngReadyLookatthisphotograph.Whatdoyouthinkisthepicture?Youmightbesurprisedtolearnthatthisisaphotographofgalaxies.Eachgalaxyismadeupofbillionsofstars.Infact,theuniversehasmorethan100billiongalaxies,andeachgalaxyhasabout100billionstars.Sotherearealotofstars.PeoplecanseeonlyaverysmallnumberofthemfromEarth.StarryNightOursunisahugeballoffirethatradiateslight.Starsarealsohugeballsoffirethatradiatelight,buttheyaremuch,muchfartheraway,whichiswhytheyseemsmaller.Likeoursun,starsshinelightinalldirecCons.SomeofthelighttravelsinthedirecConofEarth.Eventhoughlighttravelsveryfast,moststarsaresofarawaythatittakesmillionsofyearsfortheirlighttoreachEarth.So,whenyouseeastar,youcanseelightthatwasproducedmillionsofyearsago.Thismeansthatwhenyoulookatthestarrynightsky,youactuallylookintothepast.BytheCmelightreachesyou,thestarsthatproduceditmayhaveexplodedorcooleddownanddied.Itmakessensetoassumethatsomeofthestarsyouseedonotexistanymore.Planets,ontheotherhand,donotgeneratelight.YouseeplanetsbecausetheyarerelaCvelyclosetothesun,andtheyarelitbythesun.Lighttravelsfromthesuntotheplanetsandthenbouncesoffofthem.SomeofthislighttravelstoyoureyeshereonEarth.Usewhatyouhavelearnedaboutlightandsighttodrawoneormoremodelsthatexplain1. howyouseestars.

2. howyouseeplanets.

3. whyyoucannotseethestarsorplanetsonacloudynight.

TheSolarSystemTheuniversecontainsbillionsofgalaxies,butmostofthestarsyouseeintheskybelongtotheMilkyWaygalaxy.TheMilkyWaygalaxyconsistsofhundredsofbillionsofstars,oneofwhichisEarth’ssun.Peoplecallit“thesun,”asthoughthereisonlyone.Buttheuniversecontainsmanyothersuns,too.

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TheEarth’ssunisnotatthecenteroftheMilkyWay,likeitsomeCmesseemstobeinpictures.Thesunisactuallyofftooneside.Eightplanets,theirmoons,andotherobjectssuchasasteroidsandcomets,movearoundtheEarth’ssun.Alltheseobjectstogetherarecalledthesolarsystem.ThesunisthebiggestobjectinEarth’ssolarsystem.Itmakesupmorethan99%ofthesolarsystem’stotalmass.Alltheotherobjectsinthesolarsystemarearrangedaroundthesun.Theobjectsareconstantlymovinginorbitsaroundthesun.Lookatthemodelofthesolarsystem.ItshowstheposiConoftheplanetsinrelaContothesunandcomparedtoeachother.Italsoshowstheshapeofthepatheachplanetmakesaroundthesun.Thesepathsarecalledorbits.Likeallmodels,thismodelhaslimitaCons.TherelaCvesizesoftheobjectsinthemodelarenotaccurate.Forexample,inthismodel,thesunseemsabout50Cmesbiggerthantheearth,butitisactuallymorethan300,000CmeslargerthanEarth.Torepresentthesunandtheplanets’sizesaccurately,amodelofthesolarsystemwouldhavetobebiggerthanyourschool.Whatelseisnotrepresentedaccuratelyinthemodel?

DoAllScienCstsAgreeonThisModeloftheSolarSystem?ScienCstsusedtothinktherewerenineplanetsinthe

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solarsystem—theeightthatareinthediagramandPluto.Afewyearsago,scienCstsdecidedthatPlutowasnotaplanet.Why?ScienCstsbelievethatalltheplanetsinthesolarsystemoriginatedfromahugecloudofgasanddustthatusedtosurroundthesun.Forthisreason,alltheplanetshavemanythingsincommon.Theshapeoftheirorbitsisonethingtheyhaveincommon.However,Pluto’sorbitisverydifferentfromtheotherplanets’orbits.Infact,itsorbitcrossesNeptune’s,soatCmesitisfartherawayfromthesunthanNeptune,andatotherCmesitiscloser.AsscienCstscollectnewevidence,theysomeCmesrealizethatwhattheythoughtbeforewaswrong.Theychangetheirideasandtheychangetheirmodels.Thisisanexampleofhowscienceworks.Ifyoulookaroundatmodelsofthesolarsystem,youmightseesomewithnineplanetsandsomewitheightplanets.SomedayscienCstsmaygathernewevidencethatwillconvincethemthattheyneedtochangetheirmodelofthesolarsystemagain.HowDoesLightAffectWhatISeeintheSky?Whenyoulookattheskyduringtheday,youcanseethesunandsomeCmesthemoon,butyouneverseetheplanetsorthestars.Thisisbecausethesun’slightissobrightthatyoureyescannotdetectmuchweakerlighteventhoughtheweakerlightalsoreachesyoureyes.Itislikegoingsomeplacewherethemusicisloudoracrowdischeeringreallyloudly,andyoucannothearwhatyourfriendnexttoyouissaying.Normallyyoucouldhearyourfriend,buttheloudnoisemakeseveryothersoundseemquiet.Thebrightlightofthesunmakesthelightfromtheplanetsandthestarstooweakforyoutodetect.

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Lesson7–ScaBeringandReflecAonofLightLesson7.1–ReflecAon


Whatwillwedo?WewillinvesCgatewhathappenswhenlightstrikesamirrorandbouncesoffofit.

PredicAon:

WhatdoyouthinkwillhappentothelightwhenyoushineitonamirrorfromdifferentdirecCons?

ProcedurePlacetheAnglessheetsothatthethickhorizontallineisalongawallorthesideofabox.Tapethepaperdown,soitcannotmove.APachaflashlighttoarulerorametersCck,sothattheflashlightlensisabout30cmfromtheAnglessheet.Iftheflashlightcanbefocused,thenfocusthebeam,soitisasnarrowaspossible.Besuretheflashlightpointsstraightdowntheruler,andtheflashlightsitsflatonthetable.APachalightsensortoadifferentrulerormetersCck,sothatthedetectorendofthesensorisabout30cmfromtheAnglessheets.Besurethesensorpointsstraightdowntherulerandsitsflat.Theflashlightbeamshouldhitthewall(orbox)directlyabovethedoPedcenterlineontheAnglessheet.UsetapetoaPachaflatmirrortotheverCcalsurface.Besurethemirroriscompletelyflatagainstthewall.PlacetherulerandflashlightsothelightshinesdirectlyatthemirrorjustabovethedarkhorizontallineonthebaseoftheAnglessheet.PosiContheruleralongLine1totherightofthedoPedcenterlineontheAnglessheet.OnthelelsideofthedoPedcenterline,movetherulerwiththelightsensoraroundthepointonthepaperwhereallthelinesmeet.MovethesensorinthiswayunClyoufindtheposiConthatgivesthehighestlightreading.Inthedatatable,intherowforPosiCon1,drawtheplacementofthelightsensorthatgaveyouthelargestreading.Recordthenumberofthelinethatthelightsensorison.WriteanyobservaConsyoumayhavemadeasyoufoundthebiggestvalue.RepeatSteps1–3fourCmes,eachCmeplacingtheflashlightonadifferentlinetotherightofthedoPedlineandkeepingitinthatplacebutmovingthelightsensoronLines1through5tothelelofthedoPedcenterline.

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Conclusion

1. WhatpaPernsdoyounoCceinthedrawingsyoumadeinyourtable?

2. Thefollowingmodelshowslightraysastheyleaveasource.Someofthelightrayswillhitthemirror.BasedonwhatyoulearnedinthisacCvityabouthowlightbouncesoffofamirror,usearulertodrawthepatheachlightraywilltakealeritbouncesoffthemirror.

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Lesson7.2–InvesAgaAngScaBeringandReflecAon


Whatwillwedo?WewillusealightsensortoinvesCgatewherelightgoesaleritbouncesoffoftwodifferentsurfaces.ThisinvesCgaConwillhelpexplainwhyamirrorlooksdifferentfromasheetofpaper,eventhoughlightbouncesoffofboth.

PredicAon:

TodothisacCvity,usethesamesetupthatyouusedinAcCvity6.1.1. InAcCvity6.1youinvesCgatedhowlightbehavedwhenitbouncedoffamirror.Howdidthelight

sensor’sreadingschangeasyoushinedthelightonthemirrorandthenmovedthesensorfromPosiCon1through5?

2. Basedonthelightmodel,whatdoyouthinkthelightsensorreadingswillshowasyoumovethesensorfromPosiCon1throughPosiCon5whenyoushinetheflashlightonasheetofpaper?

ProcedurePreparethesetupwiththeflashlight,lightsensor,mirror,andtworulersormetersCcksjustlikeinAcCvity6.1.UsetheAnglesheetagain,asinStep1ofthatacCvity.PlacethemetersCckwiththeflashlightalongPosiCon3totherightofthedoPedcenterlineontheAnglessheet.TapethismetersCcktothetablesothatitdoesnotmoveduringthisacCvity.PosiConthemetersCckwiththesensoratPosiCon1onthelelsideofthedoPedcenterline.Recordthemeasurementfromthelightsensorinthedatatable.MovethelightsensorthrougheachposiCon(1–5)ontheAnglessheet,andrecordeachmeasurementinthedatatable.Aleryoucompletethedatatable,removethemirrorandreplaceitwithapieceofwhitepaper.Createanewdatatablejustliketheoneyouusedforlightbouncingoffthemirror.TitlethenewdatatableLightBouncingOffofPaper.RepeatSteps1–3withthelightshiningonthesheetofpaper.RecordeachmeasurementfromPosiCons1–5inyournewdatatable.

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Data

Recordthedatayoucollectabouthowlightbouncesoffofamirror.

Conclusion

1. Comparethedatayoucollectedforthemirrorwiththedatayoucollectedforthesheetofpaper.

2. HowdoyourdatacomparewithyourpredicCons?Iftheyarenotthesame,describehowyourpredicConwasdifferentfromwhatyouactuallymeasured.

3. Whatisdifferentaboutthemirrorandthepaperthatcouldexplainwhytheresultsweredifferentforeachobject?

Sensor Position Mirror Sensor Reading

White Paper Sensor Reading

1

2

3

4

5

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Lesson7.3–ScaBeringandReflecAngPart1


Imaginethatyoushineaflashlightontoamirror,asshowninthefollowingimage.Drawtwodifferentplaceswhereapersoncouldstandsothatlightbouncingoffofthemirrorwillreachthem.Addraystothemodel

Conclusion

1. Explainwhythepersoncouldstandineitheroftheseplaces.

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2. Imaginethatyoushineaflashlightontoabrickwall,asshowninthefollowingimage.Drawtwodifferentplaceswhereapersoncouldstandsothatlightbouncingoffofthewallwillreachthem.

3. Explainwhythepersoncouldstandinbothoftheseplaces.Addraystothemodel.

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Lesson7.4–ExplainingScaBering,ReflecAngandImages


Whatwillwedo?Wewilluseourlightmodeltoexplainwhywecanseeanimageofourselvesinamirrorbutwecannotseeourselvesinasheetofpaperorwood.

ProcedureThefollowingdiagramshowswhatyouseewhenyourteachercoverspartofanimagewithasheetofpaper.Thediagramshowsseverallightraysthathavebeengivenoffbyaflashlight.Baseduponthelightraysyoucansee,drawwhereyouthinktheflashlightislocated.Thefollowingdiagramshowswhatyouseewhenyourteachercoverspartofanimagewithasheetofpaper.Thediagramshowsseverallightraysthathavebeengivenoffbyaflashlight.Baseduponthelightraysyoucansee,drawwhereyouthinktheflashlightislocated.

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Conclusion

1. ExplainwhyyoucanseeyourreflecConinamirrorbutnotinasheetofpaper.

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Lesson7.5–ScaBeringandReflecAng-Part2


Whatwillwedo?WewillexplainwhatyouhavelearnedaboutscaPeringandreflecCon.ThenapplywhatyouhavelearnedbyexplainingsomethingthatyouseealltheCmebutmightnotstoptothinkabout.

ProcedureThefollowingtwopicturesshowacaronadryroadandawetroad.

Conclusion

1. WhatdetermineswhetheranobjectwillscaPerlightorreflectlight?

2. Whyisitpossibletoseeyourselfinanobjectthatreflectslight,butnotinonethatscaPerslight?

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3. UsingwhatyouknowaboutscaPeringandreflecCon,explainwithwordsordrawingswhyitispossibletoseeanimageofthecaronthewetroadbutnotonthedryroad.

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Reading7.6–PolishingObjects

Ge`ngReadyLookatthisphotograph.ItisaphotoofsomethingmagnifiedmanyCmes.Whensomethingismagnified,itappearsmuchlargerthanyoureyeseesitbyjustlookingatit.PeoplesomeCmesrefertousingyoureyeswithnomagnifyingglassormicroscopeas“seeingwiththenakedeye.”Beforeyoureadthehints,takeaguess:Whatdoyouthinkthisphotois?

Herearefourhints:1. Youcankeepclothesinsomethingmadeofit.2.Youmaybesiengonitrightnow.2. Baseballplayersuseit.3. Itgrowsoutdoors.

Didyoufigureoutthatthisisapictureofwood?WhenwoodismagnifiedmanyCmes,itlookslikeCnytubes.SomeCmesthesurfaceofwoodiscoatedsothatitlooksshiny.Abaseballbatmighthaveashinysurface.Maybeyouhaveatableathomeorinschoolwithasurfacethatshines,butyoucannotseeyourreflecConinwoodaswellasyoucaninamirror.WhydoesyourreflecConinamirrorlookdifferentfromyourreflecConinwood?

WhyCanISeeMyReflecAoninSomeObjectsbutNotinOthers?Inclass,youdidaninvesCgaConusingalightsensortotracklightfromaflashlight.Youcomparedwhatthelightdidasitbouncedoffamirrorandoffasheetofpaper.Whenlightreachesasurface,itcanbereflectedoritcanbescaPered.Youlearnedthatalerthelightbouncedoffofamirror,allofthelightwentinaboutthesamedirecCon.Alerthelightbouncedoffofasheetofpaper,itwentinmanydirecCons.ReflecConiswhathappenswhenlightbouncesoffofasurfacethatisverysmooth.Amirrorhasaverysmoothsurface.Lookatthefollowingtwomodels.Theyshowtwodifferentwaysthatlightinteractswithasurface.

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ThemodelonthetopshowslightreflecCngoffofasmoothsurface,likeamirror.SeehowallofthearrowspointinaboutthesamedirecCon?Now,lookatthemodelontheboPom.ThearrowsinthismodelpointinmanydirecCons.Thisiswhathappenswhenlightbouncesoffofpaper.Paperseemssmooth,butifyoumagnifythesurface,likethephotoofwoodatthebeginningofthisreading,youcanseethatthesurfaceisbumpy.LightbouncingoffofabumpysurfaceisscaPered.ScaPeringiswhatoccurswhenlightbouncesoffofsurfacesthatarenotsmooth.ManyobjectsthatscaPerlightfeelsmoothwhenyoutouchthem.Asheetofpaperandawoodenbaseballbatfeelsmooth.However,ifyoucouldlookatthemwithapowerfulmicroscope,youwouldseethattheirsurfacesarebumpy.IfyoucouldtakeanobjectthatscaPerslight,likeapieceofwood,andsmoothoutallthebumpsandridges,thentheobjectwouldreflectmorelightandscaPerlesslight.Theprocessofsmoothingthemicroscopicbumpsandridgesonasurfaceiscalledpolishing.HowDoesaMirrorReallyWork?Inclass,yousawamodellikethisone.Yourteachercoveredthetopofitandaskedyoutoguesswhatwasunderneaththepaper.YoumayhavebeensurprisedtoseeaflashlightpoinCngdownwardinsteadofaflashlightpoinCngupward.InthisacCvity,youlearnedhowyoucanseeanimageofsomethinginamirror.Allofthelightraysarereflectedfromamirrorsotheybouncebacktoyoureyes,andtheylookliketheyarecomingfromanobjectontheothersideofthemirror.Ifthesurfaceofthemirrorisscratched,itwillscaPermoreofthelightthathitsit.Ifthemirroristooscratchedoruneven,somuchlightwillbescaPeredthatyoucannolongerseeaclearimageinthemirror.UsingMirrorstoSeetheStarsAstronomersareonetypeofscienCstswhousemirrors.Astronomersusetelescopestoproduceimagesofstarsandplanetsthatareveryfaraway.Telescopesusespeciallycurvedmirrorstoreflectlightfromstarstowardasensor.Thesensorusesthislighttoproduceapictureofthestars.Manyobjectsintheskydonotappearverybrightbecausetheyaresofaraway.ThismeansthatveryliPleofthelightthatcomesfromthemactuallyreachesEarth.Inordertogetthebestpictures,astronomersmustuseabigmirrorthatreflectsalotoflight,soithelpstoseeevenveryfaintobjects.Asmoothmirrorproducesaclearimagebecauseitreflectsalmostallthelighttothesensor,scaPeringveryliPle.PolishingaGiantTelescopeTheHaletelescopeattheMountPalomarObservatoryinCaliforniawasthelargesttelescopeintheworldformorethan50years.ThemainmirrorintheHaletelescopeis200inchesacross.Anaverage12-year-oldislessthan60inchestall.Themirrorisaboutasbigasthreeadultsstandingontopofeachother.Themirrorisverysmooth.IfyoucouldmagnifyitsothatitwasaswideastheAtlanCcOcean,thebiggestbumpyoucouldseeonitssurfacewouldbesmallerthan5cenCmetershigh.Itisverydifficulttomakeamirrorsosmooth.Ittookabout11yearsforpeopletopolishthismirrorbyhand.

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OtherThingsPeoplePolishtoReflectMoreLightPolishedmirrorsareimportanttoastronomers.Youprobablyusepolishedmirrors,too.Peoplepolishotherobjects—likerocks—tomakethemlookmoreshinyandprePy,asyoucanseeinthesephotos.Adevicecalledarocktumblerwasusedtopolishtherocksinthephotographs.Arocktumblerhasasmallbarrelfilledwithrocks,water,andcoarsesand.Thebarrelrotatesslowlysothatthecoarsesandrubsoverthesurfaceofthebumpyrocks.Coarsesandsmoothesthelargebumpsontherocks.Thosearethebumpsthatyoudonotneedamicroscopetosee.Inthephoto,itiseasytoseethebumpsonthestonesonthelel.Alerawhile,thecoarsesandisreplacedwithfinersand.Sandthathasafinegraincansmoothoutsmallerbumpsthatyoucannotseeorfeel.AlerenoughCmeinarocktumbler,rocksandmineralsappearmuchshinierthantheywereatfirst.Why?Thepolishedrocksaresmoother,sotheyreflectmuchmoreofthelightthathitsthem.WhatMakesWoodLookShiny?Woodispolishedinadifferentway.Topolishwood,thesurfaceiscoveredwithaclearsubstance,likewax.ThewaxfillsalltheCnyholesinthewood.Alertheholesarefilled,thewoodhasasmoothsurfacethatreflectslightmuchbePer.Thefollowingpicturesshowthedifferencebetweenawoodfloorwithwaxandonewithoutwax.WhyDoPeoplePolishThings?Peoplepolishsurfacesfordifferentreasons.Theypolishwood,rocks,andmineralsbecausetheylikethewaythefinishedobjectslookandfeel.Materialslikegoldanddiamondsarenotveryshinybeforetheyarepolished.Thediamondandgoldjewelrypeoplewearhasbeenpolished.Inscience,polishingisanimportantpartofmakinginstrumentsliketelescopesworkproperly.Instrumentslikethesecanhelppeoplelearnmoreabouttheuniverseinwhichtheylive.

1. Topolishleathershoes,peopleuseshoepolish.Whatdoesthistellyouaboutthesurfaceofleather?

2. MostobjectsthatcanbepolishedsCllscaPersomelight;noobjectcanhavepurereflecConwithoutanyscaPering.Why?

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Reading7.7–MoonPhases

Ge`ngReadyCanyouimaginetravelinginaspacecralandthensteppingoutontothesurfaceofthemoon?OnJuly21,1969,theAmericanastronautNeilArmstrongbecamethefirstpersontowalkonthemoon.Asheputhisfootdown,Armstrongdeclared,“Thatisonesmallstepforman,onegiantleapformankind.”ArmstrongisoneofthefewpeoplewhohavebeenluckyenoughtoseehowEarthlooksfromthemoon.MostpeopleonlyseehowthemoonlooksfromEarth.Inthisreading,youwilllearnhowpeopleseethemoonfromEarth.Youwillalsolearnwhythemoon’sappearancechangeseveryday.Tounderstandthis,youneedtolearnwhytherearedaysandnightsonEarth.WhatMakesDayandNightHappen?Everydayyoucanseethesunasitseemstorisefromtheeasternhorizon,moveacrossthesky,andsetinthewest.WhatpeoplesomeCmesdonotunderstandisthatthesunisnotreallymovingatall.ItonlyseemstomovebecausetheEarthspinsaround,carryingpeopleinandoutofviewofthesun.Youseethesunduringthedaybecauseyouareonthepartoftheearthfacingthesun.Youdonotseeitatnightbecausetheearthhasspunsothatyouareonthesideturnedawayfromthesun.Imaginethatyouaresiengonachairthatcanspin,andafriendisstandingbesideyouholdingacandle.Asyouspinslowlyinthechair,youfirstseethecandleoutofthecornerofoneeye,movingfromthesideunClitisrightinfrontofyou.ThenitseemstomovetotheothersideunClitdisappearsbecauseitisbehindyou.Ifyoudidnotknowyouwerespinning,youmightthinkthatthecandlewasmovingaroundyouinacircle.Thesamethinghappenswiththeearthandthesun.Insteadofthechair,theearthistheobjectthatisspinning.PeopleareseatedonthesurfaceoftheearthasitpointstheminthedirecConofthesunandthenawayfromit.Thissamethinghappenseverysingleday.YouexperiencesunriseandsunsetbecauseEarthspinsonitsaxis.Soactuallythetermssunriseandsunsetaremisleading,sincethesundoesnotactuallymovearoundEarth;itjustappearstodoso.Earth’saxisisanimaginarylinethatrunsfromtheNorthPoletotheSouthPoleandthroughthemiddleoftheearth.Earthcompletesafullturnarounditsaxisonceeveryday.Thatmeansittakes24hoursforEarthtodoacompleteturn.Earth’sspinningisthereasonwhypeopleexperiencedayandnight.OnehalfofEarthfacesthesunandislitup,soitisdayCmethere.AtthesameCme,theotherhalfofEarthfacesawayfromthesun.Thesun’sraysareblocked,soitisdark(ornigheme)onthatsideoftheearth.AsEarthspinsonitsaxis,differentpartsturntofacethesunortofaceawayfromit.ThisiswhatcausespeopleonEarthtoexperiencedayandnight.

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RoundandRoundTheyGoAtthesameCmethatEarthspinsonitsaxis,italsomovesaroundthesunonapathcalledanorbit.Earth’sorbitaroundthesuntakesabout365days(oneyear)tocomplete.AtthesameCmethatEarthrevolvesaroundthesun,themoonisalsoorbiCngaroundEarth.AfullorbitofthemoonaroundEarthtakesabout28days(onemonth)tocomplete.TheseprocessesexplainwhypeopleonEarthexperiencedaysandnights,andthemoonlooksdifferentatdifferentCmesofeachmonth.Allofthesearerelatedinsomewaytolight.Thisreadingwillfocusonhowpeopleseethemoonandwhythemoon’sshapechangeseveryday.HowDoPeopleSeetheMoon?Foryoutoseeanobject,iteitherneedstobealightsourceoritneedstobelitbyalightsource.Thesunisalightsource,whichiswhyyoucanseeit.Themoon,ontheotherhand,isnotalightsource.Yet,youcansCllseeit.Theonlythingthatcouldbehappeningisthatthemoonisbeinglitbysomeotherlightsource.CanyoutellfromthemodelwhatislighCngthemoonsothatyoucanseeit?Thelightsourcethatshinesonthemoonisthesun.Halfofthemoonisalwayslitbythesun,justlikehalfoftheearthisalwayslitbythesun.Youcanneverseethedarksideofthemoon,becausenolightreachesit.Ifnolightreachesit,nolightcanbescaPeredfromittoyoureyes.ThinkaboutthefourcondiConsneededforyoutoseeanobject.HowarethesecondiConsmetinthecaseofseeingthemoonfromEarth?Lookatthediagramtohelpyouexplain.

Foryoutoseethesideofthemoonthatislitbythesun,someofthesun’slightthatisscaPeredbythemoonneedstoreachyoureyeshereonEarth.MoonriseandMoonsetWhenyouarestandingonEarth,themoonappearstomoveacrossthenightskyjustasthesunappearstomoveduringtheday.Infact,Earthspinningarounditsaxiscausesthemoontoriseintheeastandsetinthewest,justlikethesun.ManyCmes,themoonrisesduringthedayinsteadofduringthenight.Ifwelookcloselywecanseeit,butweusuallydonotnoCceit.Why?

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WhatMakesaFullMoonoraHalfMoon?Dependingonwhenyoulookatthemoon,youmightseeafullmoon,ahalfmoon,aCnysliverofamoon,ornomoonatall.Infact,themoonisalwaysthere,andhalfofitisalwayslitbythesun.WhetheryouseeitornotandwhatshapeyouseedependsontheposiConofthemooninrelaContothesunandEarth.FromEarth,youcanonlyseethepartofthemoonthatisfacingEarth.Thisisnotnecessarilythepartofthemoonlitbythesun.Thisiswhy,mostoftheCme,wedonotseeafully-illuminatedcircle,butonlypartofit.Thechangingshapethatyouseeiscalledaphaseofthemoon.ThephaseisthepartofthemoonthatisbothlitbythesunandseenfromEarth.ThephasesofthemoonchangeinacyclestarCngwiththenewmoon(alsocalledthedarkmoon).Becauseittakes28daysforthemoontogoaroundEarth,thechangingshapethatyouseerepeatsevery28days.Lookatthemodeltoseethecycleofphasesandthenamesofeachphase.Waningmeansshrinking,waxingmeansgrowing,andgibbousmeansswollen.YoumaychoosetosearchontheInternetforvideoillustraCngandexplainingthemoon’sphases.TobePerunderstandhowyouseephasesofthemoon,itmighthelptolookattwophasesmoreclosely.NewMoon(orDarkMoon)AnewmoonexistswhenthemoonisbetweenthesunandEarth.Atthatpoint,thelitsideofthemoonisfacingdirectlyawayfromEarth,soyoucannotseeit.ThesideofthemoonfacingEarthisnotlit,soitisdark.Whenyoulookinthenightsky,youmaythinkthatthereisnomoonatall.ThesunisreflecCngoffofthesurfaceofthemoon,butifyoudrewthearrowsinthepreviousdiagram,youwouldseethatnoneofthelightisreachingtheeyesofpeopleonEarth.FullMoonAfullmoonexistswhenEarthisbetweenthesunandthemoon.ItisimportantforyoutonoCcethelinesoftheorbitsforthistomakesense.RememberthatthemoonisorbiCngEarth;itisnotorbiCngthesun.WhenthelitsideofthemoonisfacingEarth,youseeabigcircleofmoonthatiscalledafullmoon.Thedarksideofthemoon(thesidethatisnotilluminatedbythesun)isfacingawayfromEarth.Becausethecycleofthemoon’sphasesrepeatsevery

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28days,itispossibletousethepreviousmodelstopredictthemoon’sphaseonanygivendate.IfyouhaveaccesstotheInternet,youcanlookupcalendarsofphasesofthemoon.Drawamodelexplainingwhythemoonwilllookthewayitwillonyournextbirthday.Ifyouarenotsure,takealookatthemodelsontheotherpagesinthisreading.Insteadofusingthecomputer,youcouldalsochooseoneofthemoon’sotherphases(notafullornewmoon)anddrawamodeltoexplainwhyitwouldlookthatwayonEarth.

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Lesson8–TransmissionofLightLesson8.1–Whydoesthemoonchange?


Whatwillwedo?WewillinvesCgatewhatcausesthephasesofthemoon.

ProcedurePart1

Pretendthataping-pongballisthemoon.Theskewerthroughtheballletsyouholditmoreeasily,butitdoesnotrepresentanything.SincetheposiConofthesunbarelychangesasthemoonrevolvesaroundEarth,itisimportantthatyoukeepthewhitehalfoftheping-pongball(thesideofthemoon)facingthesunduringthisacCvity.Holdtheendoftheskewerwiththeballturnedsothatthewhitehalfistoyourlelandtheblackhalfistoyourright.Yourarmshouldbestraightoutinfrontofyou.ImaginethatthesunisonyourlelthroughoutthisacCvity.Nowlookattheball(themoon)anddrawwhatyousee.

Nowmoveyourarm,sClloutstretched,45°tothelel,withouttwisCngtheskewer,sothatthewhitehalfoftheballsCllpointsinthesamedirecConasbefore—tothelel.Whilethemoonhasmoved45°tothelel,neithertheearth(you)northesunhave;thesunissClltothelel.ThatiswhythewhitesideofthemoonsCllhastofacelel,eventhoughthemoonhasmoved.Onceagain,lookattheball(themoon)anddrawwhatyousee.

Moveyourarm45°farther,sothatthemoonisallthewaytoyourlel.ThewhitesideshouldsCllbefacinglel,awayfromyou.Drawwhatyousee.

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PutyourarminthesameposiConyoustartedin—straightoutinfrontofyou.Now,moveit45°totheright,keepingthewhitesidefacingthelel,towardthesun.Drawwhatyousee.

Nowmoveyourarm45°totherightagain.Yourarmshouldbeouttoyourrightside.Thewhitesideoftheball—thelitsideofthemoon—shouldsCllbefacingthesun.Drawwhatyousee.

LookatReading6.4.Usethediagramtocompareyourdrawingsoftheballtothephasesofthemoon.Addthepropernamestothephasesofthemoonrepresentedinyourdrawings.

Part2ThreestudentswillparCcipateinthenextpartoftheacCvity.Onewillsitonaswivelchair.ThispersonwillbeEarth,andEarthshouldrevolveslowlytosimulateEarthspinningonitsaxis.Anotherpersonwillstandtotheside,poinCngalitflashlightatEarth.Thatpersonwillrepresentthesun.Theteacherwilldarkentheroom.WhyistheflashlightapoorsimulaConofthesun?

WhichsideofEarthisindayCmeandwhichsideisinnighemeduringthisacCvity?

Whatcausesittobedarkduringthenighteventhoughthesunisalwaysshining?

Athirdpersonwillrepresentthemoon.ThispersonwillrevolveslowlyaroundEarth.Thisvolunteershouldwalkveryslowly—muchslowerthanEarthspins.HowmanyrevoluConsonitsaxisdoesEarthcompleteintheCmeittakesthemoontogooncearoundEarth?

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Isthemoonmoreoleninthenightsky(onthenightsideofEarth)orinthedaysky(onthedaysideofEarth)?Whydowealwaysthinkofthemoonasbeingintheskyduringthenightandnotduringtheday?

Atagivenmoment,whereonEarthcanyouseethesunrising?

Conclusion

1. InthefirstpartofthisacCvity,halfofthemoonwasblackbecauseitwaspaintedblack.Inreality,whyishalfofthemoonalwaysblack?

2. Whydoesthemoonappeartohavedifferentshapesduringdifferentpartsofthemonth?

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Lesson8.2–EvaluaAngtheLightModel


Whatwillwedo?Wewillevaluateourcurrentmodeloflighttoseeifithelpsusexplainwhywecanseethroughsomeobjectsbutnotothers.

Procedure-Part1Inthefollowingspace,drawthelightmodeltoexplainwhyyoucannotseeanobjectwhenthereisacardboarddividerbetweenyoureyeandtheobject.

PredicAon:

1. Accordingtothelightmodel,whathappenstolightwhenitreachesanobject?

2. Inthatcase,whatdoesthelightmodelpredictyouwillseeifyoureplacethecard-boarddividerinthelightboxwithaclearplasCcdivider?

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Procedure-Part2Putthecardboarddividerinthelightbox.Lookattheobjectinthebox.Talkwithyourgroupaboutwhatthelightisdoingsothatyoucanorcannotseetheobject.NowreplacethecardboarddividerwithaclearplasCcdivider.Lookattheobjectagain.Talkwithyourgroupaboutwhatthelightisdoingsothatyoucanorcannotseetheobject.Whydoestheconsensusmodelnothelpyouexplainhowyouwereabletoseetheobjectthroughthetransparency?

ThelightmodelneedstoberevisedtoexplainthatyoucanseeanobjectinthelightboxthroughaclearplasCcdivider.

Drawthelightmodelsothatitexplainsthefollowing:Howcanyouseeanobjectontheoppositesideofacleardivider?Whyisitpossibletoseethecleardivideritself?

Howdoesyourdrawingshowthatitispossibletoseetheobjectthroughthedivider?

Howdoesyourdrawingshowthatitispossibletoseethedivideritself?

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Lesson8.3–MeasuringLightTransmission


Whatwillwedo?Wewillcompareournaked-eyeobservaConsoftransmissionwithmeasurementstakenbyinstruments.

PredicAon:

ProcedureUsethefollowingtabletoordertheobjectsyouhavecollectedaccordingtohowmuchlighttheytransmit.Theobjectthattransmitsthemostlightshouldbea“1”.Theobjectwiththelowesttransmissionshouldbea“5”.UsealightsensortomeasuretheamountoflighttransmiPedthrougheachobject.Recordthedatainthedatatable.Ranktheobjectsbasedonthelightsensordata.

Data

Object Prediction (1-6)

Light measurement Transmission Rank (1-6)

No object between the light source and the sensor.

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Conclusion

1. Lookatthelistsanothergroupmadefortheobjectsyoucollected.WhichlistmatchesbePer?TheonemadebyesCmaCngtheamountoftransmiPedlightwithyoureyes,ortheonemadebymeasuringlightusingthelightsensors?

2. WhataresomereasonswhymeasurementdeviceswereusefulinthisinvesCgaCon?

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Lesson8.4–RevisingtheLightModel


Whatwillwedo?Wewillusethelightmodeltopredictwhyitispossibletoseethroughsomeobjectsbutnotthroughothers.

ProcedureThefollowingdiagramshowslightleavingasourceandhiengapieceofglass.Drawwhatyouthinkwillhappentothelightraysastheyhittheglass.(Hint:Canyouseethroughglass?CanyouseeareflecConofyourselfinglass?)

Thefollowingdiagramshowslightleavingasourceandhiengapieceofunpolishedwood.Drawwhatyouthinkwillhappentothelightraysastheyhitthewood.(Hints:Canyouseethroughwood?CanyouseeyourreflecCononawoodsurface?)

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Conclusion

1. InLesson6,youlookedataphotoofpapertakenwithamicroscope.Yousawthatpaperismadeoffibers,andyoulearnedthatlightscaPersoffthesurfaceofpaper.Imaginethatapersonislookingthroughasheetofpaper,asshowninthethefollowingincompletemodel.Imaginethatthepersoncanbarelyseethelightsourcethroughthepaper.Completethemodelbydrawingarrowstoshowthis.

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Lesson8.5–TransmissionofLight


Whatwillwedo?WewillexaminemoreexamplesoftransmissionandreflecConoflight.WhenweinvesCgate,think,talk,andwriteaboutscience,weunderstanditbePer.Lightfromaflashlightisshownhiengtwodifferentobjectsbelow.1. Completeeachdiagram,sothatitshowshowmuchlightyouthinkeachobjectwilltransmit.2. MakesuretoshowwhetherlightthatbouncesofftheobjectwillbescaPeredorreflected.

ReflecAveSunglassesSomesunglasseshaveareflecCvecoaCng.ThecoaCngmakesthemlooklikeamirror,butitsCllallowsthepersontosee.

RicePaperRicepaperisusedinplaceslikeJapantomakedoorsthatletlightthrough.Thepictureshowsadoormadewithricepaper.

Conclusion

1. AlerEvacleanedtheslidingglassdooratherhouse,herfriendcameoverandwalkedrightintoit.Whyisiteasiertoseetheglasswhenitisdirtythanwhenitisclean?

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Reading8.6–UsinglightinopAcalfibers

Ge`ngReadyHaveyoueverseenalamplikethisone?ThelamphashundredsofthinplasCcfiberscomingoutofit.TheendsofthefibersglowwithaCnylight.TheseCnystrandsarecalledopCcalfibers.OpCcalfibersareusedtomakefunlamps,buttheyarealsousedinotherwaystomakeyourlifeeasier.EveryCmeyougoontheInternet,yousendandreceiveinformaConusingopCcalfibers.OpCcalfibersalsomakeitpossibleforatelevisiontogethundredsofchannels.Inthisreading,youwilllearnaboutopCcalfibersandhowtheywork.TheyareoneofthewaysthatscienCstscreatenewthings,becausetheyunderstandlight.

HowDoOpAcalFibersWork?LookaroundyourhouseforapieceofclearplasCc.YoumightfindaCDcase,asodapopboPle,orplasCcwrapfromthekitchen.NoCcethatyoucanseethroughtheclearplasCc.ExplainhowitispossibletoseesomethingontheothersideoftheplasCc,eventhoughtheplasCcisblockingthepathbetweentheobjectandyoureye.

LookcarefullyattheplasCcsurface.ExplainhowitispossibleforittotransmitlightandforyoutoalsoseeyourreflecCon.

WhatDoesPlasAcHavetoDowithOpAcalFibers?OpCcalfibersworkbecauselightisreflectedandtransmiPedbymaterialsinthefiber.MostopCcalfibersaremadeofglasssurroundedbyothermaterials.Lighttravelsintothecorebecauseclearglasstransmitslighteasily.WhatmakesopCcalfibersspecialiswhathappenswhenthetransmiPedlighthitsthesideoftheclearglasscore—itisreflectedlikeitwouldfromamirror.Becausethelightisreflected,itcanfollowalongthefiber,evenwhenthefiberisbent.ThisiswhyopCcalfibersaresomeCmescalled“lightpipes.”PeoplecandirectlightdownanopCcalfibermuchliketheycandirectwaterthroughawaterpipe.NotethepictureofabeelookingintoathickpieceofopCcalfiber.WhileitlookslikethereisanotherbeecomingoutoftheopCcalfiber,youarereallyjustseeinglightthathasbeenscaPeredfromthebee,transmiPed,anddirectedalongthebentfiber.HowDoesOurLightModelApplytoWhatHappensinOpAcalFibers?Inclass,youcreatedaconsensusmodeltodescribehowlighthelpsyousee.Inthismodel,youdrewlightasstraightlinesthatgooutinalldirecConsfromalightsource.Iflightbouncesoffanobject,itchangesdirecConsandthentravelsinastraightlineagain.Youdrewlightasstraightlinesbecausewhenlighttravelsthroughtheair,itmovesinastraightline.LightalsomovesinastraightlineinanopCcalfiber.Lightdoesnotbend;itjustseemstobendasitchangesdirecConwhenitisreflectedatthesides.Ifyoushineaflashlightintheair,thelightwillfollowastraightpathunClithitsanobject.IfyoushineaflashlightintooneendofanopCcalfiber,thelightwillfollowthepathofthecableandcome

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outtheotherend.Gobackandlookatthepictureofthelampatthebeginningofthisreading.Theendsofthefibersarebright,becauselightfromthelamphasfollowedthefibersandisleavingthemattheotherend.HowAreOpAcalFibersUseful?Youmayalreadyknowthatcomputerscommunicatewitheachotherusingelectricalwires.ComputerscanalsocommunicatebyshininglightdownopCcalfibers.Whywouldpeopleprefertosendsignalsdownafiberusinglightinsteadofdownawireusingelectricity?OnereasonisthatopCcalfiberscanbemuchthinnerthanelectricalwires.Boththewirebundleandasinglefibercandothesamejob.Asinglefibercandotheworkofmanyelectricalwires.HaveyouevertriedtoloadawebpageandhadtowaitalongCme?Thishappensbecausemanycomputersaretryingtosendsignalsdownthesamewires.Tryingtosendmanysignalsdownthesamewireisliketryingtodrivealotofcarsonthesameroad.Iftherearetoomanycarsontheroad,therewillbeatrafficjam.BecauseopCcalfibersaresmallerbutcancarrymoresignalsatonce,theycanhelptopreventtrafficjamsthathappenontheInternet.ThisiswhysomepeoplecalltheInternettheinformaConsuperhighway.NewwaysofcommunicaCngareeverywhere.Televisionhaschangedalotsinceyourparentsorgrandparentswereyoung.Askaparent,grandparent,oranotherolderpersonthefollowingquesConsabouttelevision:

• HowmanychannelscouldtheygetonTVwhentheywereyourage?• HowdidtheTVrecepConcomparetotoday?

WhydoyouthinkthesituaContodayisdifferentthanwhattheydescribed?Describewhatyoulearned.

UsingOpAcalFibers:SurgeryWhendoctorsdosurgery,theymustbeabletoseeinsideapaCent’sbody.Usually,theyhavetocutintoskin.ByusingopCcalfibers,doctorscanmakeveryCnycutsandleavescarsthatarealmostinvisible.AlermakingaCnycut,doctorsinsertasmallopCcalfiber.TheycanlightuptheinsideofthepaCent’sbodybysendinglightthroughthefiber.Whenthelighthitssomethinginsidethebody,itbouncesoffandentersasecondopCcalfiber.Thesecondcablecarriesthelighttoacamera.Thecameraproducesapicturethatthedoctorcanseeonatelevisionscreen.OpCcalfibershavemadesurgerymuchsaferforpaCents.UsingOpAcalFibers:LighAngHaveyoueverbeeninaroomwithnowindows?Manypeoplewhoworkinofficebuildingsdothiseveryday.SomescienCstsareworkingwithopCcalfiberstochangethat.BypuengoneendofanopCcalfiberoutside,itispossibletosendsunlighttoaroomthathasnowindows.OpCcalfibersmaysomedayprovidesunlightforpeoplewithnowindows,eveniftheyareunderground.OpCcalfiberscanprovidepeoplewithnaturalsunlightforfree,butwhataresomedisadvantagestousingopCcalfiberstolightaroomwithsunlight?

�92

WhyAreOpAcalFibersImportant?OpCcalfibersallowpeopletouselightforalotofnewpurposes.Peoplecansendsignalsbetweencomputers,andtheycandomuchsafersurgeries.Tosendlightdownacable,opCcalfibersrelyonreflecCngandtransmienglight.Thesearetwodifferentwaysthatlightcaninteractwithobjectsandmaterials.Inthenextlesson,youwilllearnaboutathirdwaythatlightcaninteractwithobjectsandmaterials,andyouwillbegintoimaginenewpossibiliCesforthefuture.

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Lesson9–AbsorpAonofLightLesson9.1–Lightmakesthingshappen


Whatwillwedo?WewillinvesCgateanotherwaylightcaninteractwithobjects.Lightcanalsobeabsorbed.

ProcedureYourteacherwillshowyouaradiometer,whichspinswhenlightshinesonit.

Inthefollowingtable,listotherobjectsyouhaveseenthatwhenlighthitsthem,somethinghappens.Describewhathappenswhenlightisshinedoneachobject.

Data

Conclusion

1. Theobjectsonyourlistallabsorblightandthensomethinghappens.WhichobjectsonyourlistalsoscaPer,reflect,ortransmitlight?

Object What happens when light shines on the object? v

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Lesson9.2–InvesAgaAngheaAngbylight


Whatwillwedo?WewillinvesCgatehowlightinteractswithwater.AlercollecCngdata,wewillreviseourmodelsoitcanexplainwhysunlightfeelswarm.

ProcedureAbrightlightwillbeshinedontwobeakersofwater.Onebeakercontainsclearwater,andtheothercontainswatercoloredwithfoodcoloring.Predictwhichbeakerofwaterwillgetwarmer:thecoloredwaterortheclearwater.Explainwhyyouthinkso.

AlightsensorandathermometerwillbeusedtotakeseveralmeasurementsduringthisinvesCgaCon:

amountofreflectedlightamountoftransmiPedlightstarCngwatertemperatureendingwatertemperature

Createadatatabletorecordthemeasurementsfortheclearwaterandthecoloredwater.

Data

Conclusion

1. Howdoestheamountoflightreachingthecoloredwatercomparewiththeamountreachingtheclearwater?Howdoyouknowthis?

Variable Clear Water Dark Water

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2. Thefollowingwillhelpyouuseyourdatatounderstandwhyonebeakerofwatergotwarmerthantheother.

3. AddtheamountofreflectedlighttotheamountoftransmiPedlightfortheclearwater.

4. AddtheamountofreflectedlighttotheamountoftransmiPedlightforthecoloredwater.

5. Howisthetotalamountoflightthatyoumeasured(lightthatwasreflectedandtransmiPed)relatedtotheamountofheaCng?

6. Whatdoyouthinkhappenedtothelightthatcausedthewatertoheatup?Ifithelpsyou,draw(construct)twomodelsofwhathappenstothelightinthecaseofcoloredwaterandclearwater.

Light Reflected

Light Transmitted

Total Light Measured

Light Reflected

Light Transmitted

Total Light Measured

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Reading9.3–SolarPowerPlants

Ge`ngReadyInclass,youareinvesCgaCnghowlightcanbeusedtoheatwater.Whataresomereasonspeoplewouldwanthotwaterorsteam?

Didyouknowthatsteamcanalsobeusedtogenerateelectricity?Inthisreading,youwilllearnmoreabouthowlightmakesthingshappen.Forexample,lightcanbeusedtogeneratesteam,whichcangenerateelectricity.UsingSteamtoDoThingsAlmostalloftheelectricitythatpeopleusetolightlamps,tokeepfoodcoldinrefrigerators,ortowatchtelevisionisgeneratedbyamachinecalledasteamturbine.Youdonothaveasteamturbineinyourhome.Somewhere,atsomepowerplant,asteamturbinegenerateselectricityandsendsitthroughwires.Asteamturbineisamachinewithgiantfanbladesinside.Whenthefanbladesturn,themachineusestheturningmoContogenerateelectricity.Thetrickistofigureoutawaytomakethefanbladesturn.Youcanthinkofthebladesinsideasteamturbinelikeagiantpinwheel.Whenyoublowonapinwheel,theairyoubreatheouthitsthebladesofthepinwheelandmovethem.Now,imaginethatyoucouldholdthepinwheelaboveapotofboilingwater.Thesteamwouldalsomakethepinwheelturn,justlikewithyoublowingonit.Makingapinwheelturnbyholdingitaboveboilingwateristhesameideaasusingsteamtoturnthefanbladesinsideasteamturbine.Longago,someoneneededtofigureouthowtoheatwaterenoughsothatitturnstosteam.Thenthesteamcouldoperatetheturbineandgenerateelectricityforpeople’shomes.MostoftheelectricitygeneratedintheUnitedStatesisproducedbycoalpowerplants,whichburncoaltoheatwaterunClitbecomessteam.SolarPowerInclass,youareinvesCgaCnghowlightfromalightbulbcanbeusedtoheatwaterinabeaker.Somepowerplants,calledsolarpowertowers,uselightfromthesuntoheatwaterunClitbecomessteam.Asolarpowertowerusesthousandsofmirrorstoreflectlightfromthesuntoatowerthatholdswater.Lookatthephototoseehowthislooks.Whenlightreflectedbythemirrorshitsthetower,thewaterinsideisheated.Ifthewaterisheatedenough,itbecomessteam.Thesteamistransportedthroughpipestoasteamturbine,whichproduceselectricity.Onedrawbackofasolarpowertoweristhatitcanonlyheatwaterduringtheday.Oncethesteamcoolsdownandbecomeswateragain,itcannotturnthesteamturbines.PeoplesCllneedelectricityatnightorwhenthesunisblockedbyclouds.ToproduceelectricityattheseCmes,somesolarpowertowersheatadifferentliquidinsteadofheaCngwater.Oncethefluidisheated,itcanbetransportedthroughpipestocomeincontactwithacontainerofwater.There,itheatsthewatertomakesteam.IttakesthespecialfluidalongCmetocooldown,soitcanremainveryhotthroughout

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thenight.Becausethefluidstayshot,itcanheatwatertocreatesteamevenwhenthesunisnotshining.SolarChimneysAnotherwaytouselightfromthesuntogenerateelectricitydoesnotinvolveheaCngwateratall.Inasolarchimney,lightfromthesunheatstheairunderneathalargeglassroof.Thehotairrisesandisforcedthroughagiantchimney.Astheheatedairrises,itturnsfanbladestogenerateelectricity.Thesuncanonlyheatairduringtheday,sosolarchimneyshavepipesfilledwithliquidthatremainshotatnight.Thatmeansthesolarchimneyworksevenwhenthesunisnotshining.Lightfromthesuncanheatanobjectwhenithitsit.Thisiswhyyourskinfeelswarminthesunlight.IntheinvesCgaConyouaredoinginclass,youwilldeterminehowlightheatsthingsandwhysomematerialsgethotfasterthanothers.Thelightyourteacherusestoheatbeakersofwateriscalledafloodlamp.NoCcethatafloodlamphassilversidesdesignedtoreflectlight.Inwhatwaydoesthefloodlampworktoheatwaterfasterthanaregularlightbulb?

YouhavelearnedthatlightcanbescaPered(orreflectediftheobjectissmooth)ortransmiPedwhenitreachesanobject.Inclass,youusedlighttoheattwobeakersofwater.IfallthelightthatreachedthebeakerswasscaPeredorreflected,howhotwouldthewaterbe?

HowhotwouldthewaterbeifallthelightreachingthetwobeakershadbeentransmiPed?

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Lesson9.4–KeepingTrackofLight


Whatwillwedo?Wewillreviseourlightmodeltoaccountforallthreewaysthatlightcaninteractwithobjectsandmaterials.ObjectscanreflectorscaPer,transmit,andabsorblight.

ObservaAons

DuringthelastacCvity,youinvesCgatedwhathappenedasabeakerofclearwaterandabeakerofcoloredwaterwereheatedusinglightfromafloodlamp.Basedonwhatyousawinthatexperiment,answerthefollowingquesCons.1. WhichbeakertransmiPedmorelight?

2.Whichbeakerreflectedmorelight?

3.Whichbeakerabsorbedmorelight?

4.Whatevidenceshowedwhichbeakerabsorbedmorelight?

Conclusion

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1. Thesediagramsshowtwoincompletemodelsinwhichlightisleavingafloodlampandtravelingtowardabeakerofwater.CompletethefollowingmodelsbydrawingaddiConallightraysthatcanbeusedtoexplainyourobservaCons.Makesureofthefollowing:

• Yourmodelsshowthesameamountoflightreachingbothbeakers.• Onemodelshowsdifferentamountsoflightbeingreflected,transmiPed,andabsorbedthanthe

other.

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Lesson9.5–RevisiAngphenomenacausedbylight


Whatwillwedo?WewillexaminehowdevicesusereflecConorscaPering,transmission,andabsorpContomakethingshappen.

ProcedureLookattheobjectyourteachershowsyou.Doestheobjectreflect/scaPeralotoflight?Howdoyouknow?

Doestheobjecttransmitalotoflight?Howdoyouknow?

Doestheobjectabsorbalotoflight?Howdoyouknow?

Conclusion

1. InseveralacCviCesyousawthatlightwasscaPered,transmiPed,absorbed,orsomecombinaConofthese.IntheacCvitywiththeclearandcoloredwater,yousawthatthemorelightthatwasabsorbed,thelessthatwasscaPeredandtransmiPed.IsthisrelaConshiptruefortheobjectyourteacherjustshowedyou?MakeageneralruleaboutthewaytheamountsoflightreflectedorscaPered,transmiPed,andabsorbedbyanyobjectarerelatedtoeachother.

2. Ifyoudesignedadevicethatuseslighttomakesomethinghappen,likeheaCngsomething,makingsomethingmove,orgeneraCngelectricity,wouldyouwantmostofthelightthatreachesthedevicetobereflected,transmiPed,orabsorbed?Why?

�103

�104

Lesson9.6–AbsorpAonofLight


ProcedureApplywhatwehavelearnedaboutlighttosituaConsthathappenoutsideofscienceclass.Twopotatoesarelelinthesunshineforanhour.Onepotatoiscoveredwithaluminumfoil.Theotherpotatohasnothingcoveringit.Alertheendofthehour,whichpotatowillbewarmer?Explain.Asolarcelluseslightfromthesuntorunelectronicdeviceslikecalculators.SolarcellshaveacoaCngthatreflectsasliPlelightaspossible.Whywouldthisbeimportant?Lightfromthesameflashlightisshinedonseveralobjects.Alightdetectormeasuresthelightalerithitseachobject.Usethefollowingdatatodeterminewhichobjectabsorbedthemostlight.Whichobjectabsorbedthemostlight?Explain.

Conclusion

1. Whichobjectabsorbedthemostlight?Explain.

2. WhichobjecttransmiBedthemostlight?Explain.

Object Light Scattered Light Transmitted

T-Shirt 131 Lux 14 Lux

Cardboard 180 Lux 2 Lux

Ice Cube 450 Lux 100 Lux

Brick 157 Lux 0 Lux

�106

Reading9.7–SolarEnergy

Ge`ngReadyHaveyouevergoneintoaroomwherethesunwasshiningbrightlythroughthewindows?Ifso,howdidthetemperatureinthisroomcomparetothetemperatureofotherrooms?Inclass,youlearnedthatlightcaninteractwithobjectsinthreeways.Lightcanbereflected(orscaPered),transmiPed,andabsorbed.Whenlighthitsanobject,one,ortwo,orallofthesecanhappenatthesameCme.Whenlightfromthesunreachesaclearwindow,someofthelightisreflectedoffofthesmoothglass.Someofthelightisabsorbedbytheglass,butmostofthelightistransmiPed.MostofthelightconCnuestotravelunClitreachesanobjectintheroom,likethefloor,walls,orfurniture.TheseobjectsthenscaPer,transmit,andabsorbthelightthatreachesthem.Thelightabsorbedbytheobjectscausesthemtoheatup.Theseheatedobjectscanthenheatotherstuffintheroom,suchastheair,theceiling,andevenyou.Today,youwillreadaboutmanywaysthatpeopleusesunlight,becausetheyunderstandthatlightcanmakethingshappen.HowDoPeopleUseReflecAon?Haveyoueverseenabuildingthatlooksasifitweremadeoutofmirrors?ThesebuildingsaremadeusingreflecCveglass.HowwouldreplacingclearwindowswithreflecCveglassaffectthetemperatureinsidethebuilding?Explainyourideas.

Inclass,yousawthatlightcancausemanytypesofchangesinobjectsbesidesheaCngthem.Lightmakesplantsgrow,radiometersspin,andlight-sensiCvepaperchangecolor.Youlearnedthatinorderforthesechangestooccur,lightreachingtheobjectmustbeabsorbed.Lightcarriesenergyasittravels,sowhenlightisabsorbedbyanobject,energyistransferredfromthelighttotheobjectthatithits.Itisthetransferofenergythatenablesobjectstoheatup,spin,grow,orchangecolor.Theenergycarriedbythelightfromthesuniscalledlightenergyorsolarenergy.Solarenergycanbeusedinmanyways.

SolarWaterHeatersSolarenergyiswidelyavailableinCaliforniabecauseitisverysunny.PeoplewholiveinCaliforniahavebeenusingsolarenergyfromthesunforalongCme.Somepeopleusesolarenergycarriedbylightfromthesuntoheattheirwater.Solarwaterheatersareolenplacedonroofstoabsorbsunlightdirectly.PeopleinsouthernCaliforniahavebeenusingsolarwaterheatersforoverahundredyears.Byusingsolarenergy,peopledonotneedtopayforthegasorelectricitythatpowermostwaterheaters.Mostsolarwaterheatershavethreeparts:ahotwaterstoragetank,asolarcollectorthatabsorbslightfromthesun,andabackupgasorelectricheaterthatcanheatthewaterincaseofacloudyday.Lookatthepictureofthesolarwaterheater.ItisdesignedtoabsorbasmuchlightaspossibleandreflectasliPlelightaspossible.

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ThinkoftheacCvityyoudidinclasswhenyouusedalightbulbtoheatabeakerofclearwaterandabeakerofcoloredwater.UsewhatyoulearnedfromthatacCvitytohelpyouexplainwhyitisbestforsolarcollectorstobeblack.

Doyouthinkusingsolarwaterheaterswouldbeagoodideawhereyoulive?Why?

HowDoesSolarEnergyMakeElectronicsWork?HeaCngwaterisnottheonlywaytousesolarenergy.Haveyoueverseenasignthatlooksliketheoneinthephotograph?Togetpeople’saPenCon,lightsflashaboveandbelowthesign.Theselightsneedelectricitytooperate,buttheydonotneedtobepluggedin.Thedarkpanelontopofthesigniscalledasolarcell.Itissimilartothesolarcollectorsyoujustreadabout.Asolarcellproduceselectricitybyusinglightenergyfromthesun.Solarcellsareusefulforthingsthatneedelectricitybutarenotnearanelectricaloutlet.StateslikeNewMexicoandArizonausealotofsolarcellsbecausetheyhavealotofsunlight,andmanydesertareasarefarfromelectricity.Solarcellsarealsousefultomovethings.Forexample,scienCstscanbuildcarsthatneverneedgasoline.Thesecarshavesolarcells,sotheymoveusinglightenergyfromthesun.SolarPanelPowersCalculatorSomecalculatorsaredesignedtooperateusingasmallsolarcell.Likethesolarcollectorsonsolarwaterheaters,solarcellsaredesignedtoabsorbalotoflightandtoreflectveryliPle.Explainwhyagoodsolarcellabsorbsalotoflightandreflectsasmallamountoflight.Someminiaturecarscanrunusingsmallsolarcells,butthesolarcellsneededtorunarealcarmustbeverylarge.Usingwhatyouknowaboutsolarenergy,explainwhyarealcarneedsabiggersolarcellthanaminiaturecar.Solarenergycanbeusedtoheatwater,generateelectricity,movethings,orevenmakelivingthingsgrow.SinceitisplenCful,anditdoesnotcreatepolluCon,solarenergyisanexcellentenergyresource.YoumaywanttolearnmoreaboutsolarenergyontheInternet.

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Lesson10–Whatistheoppositeofwhitelight?Lesson10.1–Mixingoflightwithprojectors


Whatwillwedo?WewillexplorelightandcoloranddifferentcolorsoflightinordertoanswertheDrivingQuesCon.

ProcedureToday,youwillexplorelightandcolorusingprojectorsorflashlights.ItisimportanttomakecarefulobservaConsduringeachstepoftheinvesCgaCon.Explainwhythescreenlooksbrighterwhenaprojector(orflashlight)isshiningonitthanwhenitisturnedoff.Itisnotenoughtosaythatmorelightisshiningonit.Usethelightmodeltoexplaintheamountoflightreachingthescreenandyoureyes.(Youmayalsodrawthemodelifthatwouldbehelpful.)

Whatdoyouseeonthescreenwhenaredfilterisplacedontheflashlightortheprojectorprojectsredlight?

Predictwhatcoloroflightyouwillseeonthescreenwhenyourteacheraimsthreeprojectorsorthreeflashlights(red,green,andblue)sothattheirsquaresorcirclesareoverlapping.

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Conclusion

1. Explainwhyyousawthecoloryoudidwhenallthreecolorsoflightwereoverlapping.

2. Whenyoumixdifferentcolorsoflight,thenewcoloryouseeisbrighterthantheoriginalcolorsyoumixed.Explainwhythishappens.

�110

Lesson10.2–Mixingcolorsoflightonacomputer


Whatwillwedo?WewillusetechnologytoinvesCgatehowmuchred,green,andbluelightshouldbemixedtocreatewhite,black,andshadesofgray.

ProcedureGotothefollowingwebsite:hPp://www.exploratorium.edu/exhibits/mix_n_match/(ordoawebsearchfor“Exploratoriummixnmatch”.NoteyouwillneedtobeabletorunShockwaveonyourcomputer,anditwillnotrunonaniPad).ClickonMix-n-Match.ReadtheinstrucConsonthewebsiteabouthowtoinvesCgatemakingdifferentcolorsbycombiningred,green,andbluelight.Makesureeachstudentinyourgrouphasatleastoneopportunitytooperatethecomputer’smouse.StudentswhoarenotoperaCngthemouseshouldmakesuggesConsabouthowtogetthedesiredcolor.InvesCgatewhitelight.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtocreatewhitelight?RecordyourpredicConsbeforeyoutryit.

ManipulatethecomputerunClyousucceedinmakingwhitelight.Recordyourresults.

WhydoyouthinkthisparCcularcombinaConmakeswhitelight?

InvesCgateblacklight.a.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtocreateblacklight?RecordyourpredicConbeforeyoutryit.

�111

ManipulatethecomputerunClyousucceedinmakingblacklight.Recordyourresults.

WhydoyouthinkthisparCcularcombinaConmakesblack?.

InvesCgaCnggraylight.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtoobtaingraylight?RecordyourpredicConbeforeyoutryit.

ManipulatethecomputerunClyousucceedinmakinglightgraylightanddarkgraylight.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtoobtainlightgraylight?Howmuchisneededtoobtaindarkgraylight?

WhydoyouthinktheseparCcularcombinaConsmadetheseshadesofgray?

Conclusion

1. Computerscanonlyemitred,green,andbluelight.Yet,yourcomputerscreenshowsapicturewithgreengrass,abluesky,ayellowsun,andabrownhouse.Howdoyouthinkthescreenmakesthesedifferentcolors?

�112

Lesson10.3–Howdocolorsensorswork?


Whatwillwedo?Wewilllearnhowtheeyeanddigitalcamerasdetectdifferentcolorsoflight.Wewillalsolearnwhymixturesofcolorsoflightappeartooureyestobenewcolors.

ProcedureLookattheimagesthatdescribethestructureoftwothings:thehumaneyeandadigitalcamera.Usethespaceprovidedtotakenotes.

Adigitalcameraisliketheeye—atitsbackisadevicecalledaCCDthathasthreedifferenttypesofcellsthatdetectred,green,andbluelight.

WhatarethetwotypesofcellsinthereCnaofaneye?

Eachtypeofconecelldetectsadifferentcoloroflight.WhatarethethreecolorsoflighttheconecellsinthereCnaaresensiCveto?

Whenyouareinadark,butnotcompletelydarkroom,itisimpossibletodetectthecolorsofobjectsintheroom.Everythingseemstobedifferentshadesofgray.Explainwhyyoucanonlyseeshadesofgray.

HowisthedesignoftheCCDofadigitalcamerasimilartothereCnaofthehumaneye?

�113

Youhavelearnedthattheeyeisalightsensor.AnswerthesequesConsabouttheeye:

Howdolightraysentertheeyewhileseeing?

Whydoesthepupilopenwideinthedarkandnarrowdowninbrightlight?

Whydoesthepupillookblack?

Conclusion

1. Whenamixtureofredandgreenlightentersyoureyes,youperceivethemixtureasyellowlight.Explainwhyyoureyeperceivesthismixtureofredandgreenlightasyellow.

�114

Reading10.4–Makingcolorphotographs

Ge`ngReadyHaveyoueverseenablackandwhitemovie?Didyoueverwonderwhyoldmovieswerealwaysinblackandwhiteinsteadofincolor?Alerall,everythinginthemoviewasactuallycolored.Today,youwillreadabouthowcamerasmakepicturesincolor.Whatyoulearnedinclassaboutcolormixingcanhelpyouthinkaboutmoviesandaboutphotographs.WhatHappensWhenIMixColorsofLight?Inclass,youlearnedhowtheeyedetectscolors.Youalsolearnedthattwothingshappenwhenyoumixedcolorsoflight.First,whenyoumixedcolors,youendedupwithanewcolor.Usingtwosources,youmixedredlightwithgreenlightandgotyellow.Whenyouaddedbluelightfromathirdsource,yougotwhite.Second,whenyoumixedcolorsfromtwosources,thenewcolorwasbrighter.Thecolorinthearealitbyallthreesourceswasthebrightestofallthecolors.YoumightalsohaveusedacomputersimulaConontheInternettoseethatwhenevertwocolorsoflightaremixed,thenewcolorisbrighterthantheoldones.Thishappensbecauseasyouincreasedtheamountoflight,morelightwasavailabletoreachyoureyes.OntheInternet,ifyouseeasimulaConabout“mixinglight”or“mixingcolorsoflight,”youwillseethatwhenyoumixmaximumamountsofred,green,andbluelight,youseewhite.Ontheotherhand,whenyoumixnored,green,orbluelight,youseeblack.TheseacCviCeshelpyoulearnthatwhitelightisthebrightestofallcolors,anditisamixtureofmanycolors.Whenyouseeblack,itmeansthatthereisnolightpresent.Whydoyouthinkashadowisblack?

HowDoPeopleSeeDifferentColors?InthepreviousacCvity,youlearnedhowpeopleseedifferentcolors.ThereCna,inthebackoftheeye,containscellsthataresensiCvetolight.TwokindsofcellsareinthereCna:cone-shapedcellsandrod-shapedcells.Therod-shapedcellstellyouhowbrightorhowdarksomethingis.Thethreedifferentkindsofcone-shapedcellsareeachsensiCvetoadifferentcoloroflight.SomearesensiCvetoredlight,sometogreenlight,andsometobluelight.Allthesecellssendsignalstoyourbrain.Yourbrainprocessesthesesignalsasimages.InLesson9,youlearnedaboutdigitalcamerasandfoundoutthattheyworkmuchlikeyoureyes—theydetectthelightcomingintothem.Somecamerasusefilminstead.Cameraswithfilmalsodetectthelightcomingintothecameraandtothefilmtorecordit.Youmayhavetakenpicturesonacamerathatusesfilm.Onceyouhaveusedupyourfilm,youhavetotakeittoastoretobe

�115

developed.Onlythencanyouseethepicturesthatyoutook.HowDoesFilminaCameraRecordDifferentColorsofLight?Justlikeyoureyes,acamerahasaholethatletslightinside.Inyoureye,thisholeisyourpupil.Inacamera,thisholeistheshuPer.WhenyoupressthebuPontotakeapicture,youopentheshuPer.Inasplitsecond,lightentersthecameraandtravelsthroughit.ThelightreachesthebackofthecamerawheretheCCDislocated.Inacamerathatusesfilm,thisiswherethefilmislocated.Thefilmabsorbslightwhichcausesittochangecolor.Redlightcausesthefilmtochangeinadifferentwaythanbluelight.Inblackandwhitefilm,allcolorsoflightwillcausethefilmtochangeinthesameway.Insteadofproducingareaswithdifferentcolors,blackandwhitefilmonlyproducesareasthatarelighterordarker.Colorfilmismadeofthreelayers.TheselayersoffilmareliketheconecellsinthereCnaofaneye.Somelayerssenseredlight,othersgreenlight,andothersbluelight.ThedifferenceisthatinthereCna,thedifferentconecellsarelocatedsidebyside,andinfilmthedifferentlayersareoneundertheother.Ifcolorfilmishitbyredlight,thelayerthatissensiCvetoredlightdoesnotbecomered—itbecomeslightblue.GreenlightmakesthelayersensiCvetogreenlightbecomelightpurple.BluelightmakesthelayersensiCvetobluelightbecomeyellow.Soifyoulookatfilmalerithasbeenexposedtolight,whatyouwillseewilllookverydifferentfromtheobjectthatyoutookapictureof.Itwillhavethesameshape,butallthecolorswillbewrong.Thisphotoshowswhatfilmwouldlooklikeifyoutookaphotoofacastle.ItisinteresCngtolookatthenegaCvesfromfilmthathasbeendevelopedtoseethedifferencebetweenthenegaCvesandthephotos!Alerphotoshavebeentaken,filmneedstobeprotectedsoitwillnotgetexposedtoanymorelight.FilmcansCllabsorbmorelight.Ifmorelightweretostrikethefilm,itwouldrecordthislightaswellasthelightthathititwhiletakingthepictures.Thiswouldmessupthefirstpictureitrecorded.Thefilmisrolledandplacedintoacanisterthatdoesnotletinanymorelight.ThepersonwhodevelopsthefilmopensthecanisterincompletedarknessandputsthefilmintoaliquidthatmakesthefilmnolongersensiCvetolight.Thefilmcanthenbetakenoutintotheopenwithoutanyworryofmessingitup.Thestorethenusesthefilmtoprintphotos.Themachinethatprintspicturesonfilmchangesthecolorsonthefilmbacktotheoriginalcolors,sothephotoslookliketheoriginalobjects.2.Whydoyouthinkthereisaneedforthreelayersinafilm?

3.Whydoyouthinkthelayersinthefilmneedtobetransparenttoallcolorsotherthantheoneitabsorbs?

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HowDoesaTelevisionShowColors?Sometelevisionshave“guns”nearthebackthatsendCnyparCclescalledelectronstowardthescreen.Magnetsinsidethetelevisioncanpushorpulltheelectronsup,down,lel,orright,sothattheycanhitthescreenanyplace.Theinsidesurfaceofatelevisionscreeniscoatedwithverysmalldots.Whenanelectronhitsadot,itmakesaweakflashoflight.Therearethreedifferentkindsofdots,andeachonegeneratesadifferentcoloroflight.Bycontrollingwhichdotsarehitbyelectrons,someonecancontrolwhichcolorsoflightaremadebythescreenateachpointonthescreen.AsyoulearnedinLesson9,youreyesperceivedifferentmixturesofred,green,andbluelightasnewcolors.Sincethedotsonthescreenmakingthelightaresosmall,youcannottellthemapart.WhentwodotsnexttoeachotherlightupatthesameCme,youseeonlyoneflashoflight.Thecolorofthatlightwilldependuponthecolorsoflightmadebythedots.Youhavelearnedhowcamerafilmandtelevisionscombineonlythreecolorsoflighttomakeallthecolorsthatyoureyecansee.Forexample,youknowthatredandgreenlightcanmixtomakeyellowlight.ThinkofitnextCmeyouseesomethingyellowlikeaflower.Areyouactuallyseeingyellowlight,orisitamixtureofredandgreenlightthatlooksyellowtoyoureyes?Inthenextlesson,youwilllearnhowyoucantellwhetheryouareseeingapurecolororamixtureofdifferentcolorsoflight.

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Lesson11–Howdoobjectschangethecoloroflight?Lesson11.1–AnalyzingcolorcomposiAon


Whatwillwedo?Wewilllearnhowtoanalyzelighttodetermineoutofwhichothercolorsoflightitiscomposed.

ProcedureYourteacherwillprojectawhitelineonthescreen.Explainwhythelineappearstobewhite.

WhenyourteachercoverstheprojectorwithapieceofC-Spectra,twocolorfulimagesarecreated.Eachimagecontainsallthecolorsoftherainbow.Makealistofthecolorsthatyousee.

Explainhowyouthinkdifferentcoloredobjectsthatdonottransmitlight,likeaballoratable,colorthelightthattheyscaPerorreflect.Drawamodelifithelpsyou.

UsingapieceofC-Spectra,onepersoninyourgroupshouldlookatthecoloredlineonthesheetofblackpaperthatyourteachertapestotheboard.Thispersonshouldcheckinthetablethecolorsthattheycansee.Then,whentheteachertapesadiffer-entsheettotheboard,adifferentstudentshouldanalyzethenewline.Everypersoninyourgroupshouldhavetheopportunitytoanalyzeatleastoneline.

ColorsofLight

Red Orange Yellow Green Blue Violet

Red Line

Orange Line

Yellow Line

Green Line

Blue Line

Violet Line

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ExplainwhyyouthinkthedifferentcoloredlinesscaPerdifferentcolorsoflight.

Whydoyouthinkthecoloredlineswereprintedonblackpaperratherthanonwhitepaper?

Conclusion

1. Whatcolordoyouthinkyouwouldhaveseeniftheredstripehadbeenilluminatedbyredlight?Explainyourideas.

2. Whatcolordoyouthinkyouwouldhaveseeniftheredstripehadbeenilluminatedbygreenlight?Explainyourideas.

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Reading11.2–Rainbows

Ge`ngReadyHaveyoueverwonderedwhyrainbowsappear?YouhaveprobablynoCcedthatrainbowshavesomethingtodowiththeweather.Youhaveprobablythoughtaboutthefactthatthewordrainbowhasraininit,andthatiswhenyouseerainbows.However,youdonotseearainboweveryCmeitrains.Thisreadingisaboutwhatmakesrainbowsappearinthesky.ThinkofaCmewhenyouhaveseenarainbow.TrytorememberwhattheweatherwaslikeattheCme.ThesethreequesConsmighthelpyou:• WasitsCllrainingorhadtherainstopped?• Wasthewholeskycloudy?• Wasitduringthedayornight?

YouCanMakeYourOwnRainbowBeforereading,hereisanacCvityyoucandotocreateyourownrainbow.Youneedtodothisonasunnyday.First,findawindowwherethesunisshiningin.Second,pullatableclosetothewindow.Third,placeafullglassofwaterontheedgeofthetablewherethesunisshiningthebrightest.Lookatthefollowingdiagramtoseehowtosetupyourexperiment.Onceyouplacetheglassonthetable,lookatthefloorneartheglass.Youshouldseearainbowonthefloor.Ifitisnotasunnyday,youcansClltrytomakeyourownrainbow.Makearoomasdarkaspossibleandsetupafullglassofwaterontheedgeofatable.Insteadofsunlight,youneedaflashlight.Turnontheflashlightandpointitattheglass,asiftheflashlightwerethesun.Keeptheflashlightpointedattheglass,butmovetheflashlightaliPleataCmeunClyouseearainbowonthefloororonthewall.Inthislesson,youwilllearnhowdropsofwaterandsunlightworktogethertoformrainbows.InLesson9,youlearnedthatwhitelightisamixtureofallthedifferentcolorsoflightthatyoucansee.Red,orange,yellow,green,blue,indigo,andviolet(ROYGBIV)canallbefoundinwhitelight.However,whenyouseewhitelight,youdonotusuallyseethosecolors.Inordertobeabletoseeallthecolorsthatmakeupwhitelight,youwouldhavetobreakwhitelightapartintoitscolorcomponents.ThatiswhatyoudidinLesson10,usingC-Spectra.UsingaPrismAprismisanotherwaytobreakwhitelightintoitscolorcomponents.AprismisatriangularpieceoftransparentglassorplasCc.Abeamofwhitelightshiningononesideoftheprismwillcomeoutontheothersidebrokenupintoitscolorcomponents.Thisfigureshowshowwhitelightenteringtheprismcomesoutintheformofarainbow.Nowyouknowthataprismseparateswhitelightintocolorsandyouknowthatthecolorslooklikearainbow.YousClldonotknowhowarainbowisformed.Whenlightentersaprism,theprismcausesthelighttobendveryslightlyortochangedirecConsjustaliPlebit.ThisbendingiscalledrefracCon.Notalllightgetsbentinthesameway.Somecolorsoflightgetbentmorethanothers.Thecoloroflightthatgetsbentthemostisblue,whilethecoloroflightthatgetsbenttheleastisred.Lookagainatthefigureoflightbeingrefractedbyaprism.Canyouseethatbluegetsbentmorethanred?Becausethedifferentcolorsoflightbenddifferently,theycomeoutoftheprismatdifferentplacesandmoveoutofitindifferentdirecCons.BecausetheymoveindifferentdirecCons,theyspreadawayfromeachother.Thatiswhyyoucanseethemseparately—thecolorsarenolongermixed

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together.Whatyouseeisanareainwhichthecoloroflightchangesgraduallyfromonetoanother.Itlooksjustlikearainbow.HowAreRealRainbowsFormed?Inarealrainbow,raindropsintheairactlikeverysmallprisms.Lightenterstheraindropsandgetsbentbythem.Eachcoloroflightisbentslightlydifferently.Somecolorsgetbentabitmore;othersgetbentabitless.However,unliketheprism,wherethelightcomesinonesideandleavesonanother,thelightenteringaraindropisreflectedbackatthefarsideoftheraindrop.Lookthedrawing.Thelightreturnstothesamesideoftheraindropitenteredfrom,andthenitexits.ThelightthatleavestheraindropmovesinmanydifferentdirecCons,andeachcolormovesinapredictabledirecCon.RefracConbreaksthelightenteringtheraindropintocolorcomponents,justlikeintheprism.TherefracConofthelightbytheraindropscausesthecolorstospreadouttocreateasemicircleofcolorinthesky,orarainbow.HaveyounoCcedthatthesunisalwaysbehindyouwhenyoulookatarainbow?Thinkaboutthemodeloflightthatyoudevelopedinclasstohelpyouexplainwhythesunmustbebehindyouforyoutoseearainbow.ASpecialPhenomenon:DoubleRainbowsPerhapsyouhaveseenadoublerainbowlikeinthisphoto.Thebrighterrainbowiscalledtheprimaryrainbow.Thefainterrainbowiscalledthesecondaryrainbow.Thesecondaryrainbowismadewhenlightisreflectedtwiceinsidetheraindrop.BecauseofthedoublereflecCon,thelightleavestheraindropatadifferentangle,soyouseethesecondaryrainbowhigherup.Ifyoulookcloselyatthepicture,youwillalsonoCcethatthecolorsofthesecondaryrainbowareintheoppositeorderofthecolorsintheprimaryrainbow.ThedropsofrainhavetobejusttherightsizetocreatetworeflecCons.Thisdoesnothappenveryolen,sodoublerainbowsareararesighttosee.Howcouldyouexplainhowrainbowsareformedtosomeonewhoisnotinyourscienceclass?Forexample,howcouldyouexplainrainbowstosomeoneathome?Orhowcouldyouexplainrainbowstosomeoneyoungerthanyou?Thinkaboutthatpersonasyouraudience,andexplainhowrainbowsareformedinawaythatpersonwouldunderstand.Youmightfindithelpfultodrawamodeltoexplain.

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Reading11.3–LunarEclipses

Ge`ngReadyEverydaythesunappearstoriseintheeast,goacrossthesky,andthensetinthewest.Everymonththemoongoesthroughitsphasesfromnewmoontofullmoonandbackagain.ItallseemssoorderedunClsomethingunexpectedhappens.OnenightthemoonrisesfullandbeauCful,butthen,withinafewminutes,itstartstochange;itgetsdarkeranddarker,unClitdisappears.Thenitturnsred.Alunareclipseoccurs.OurancestorswereinCmidatedbythesightofalunareclipse.Theycouldnotunderstandwhatwashappening—theyfearedtheendoftheworldwascoming.Theyprayedandbeggedforthemoontoreturn.Today,thankstoadvancesinscienCficknowledge,weknowwhatcausesalunareclipseandwecanenjoyitsbeauty,knowingitisanaturalphenomenonwhichdoesnotcauseanyharm.Inthisreading,youwilllearnaboutlunareclipses:why,when,andhowtheyhappen.Earth’sShadowAlunareclipsetakesplacewhenthereisafullmoon.YoulearnedbeforethatafullmoonexistswhenEarthisbetweenthesunandthemoon.Ifyoulookcloselyagainatthemodelshowingthephaseofafullmoon,youwillnoCcesomethingthatdoesnotmakesense.Ifthesun,theearth,andthemoonareallalignedandthemoonisexactlybehindEarth,howdoesthemoongetlitbythesun?Shadowsareactuallydarkareascausedbyanobjectblockinglight.Earthisanobjectthatblocksthesun’slight;thereforethereisashadowedareabehindEarth.Whydoestheearthnotalwaysblockthesun’slightfromreachingthemoon?IsthemoonnotinEarth’sshadow?ThetruthisthateveryonceinawhileEarthdoesblockthesun’slightfromreachingthemoon,andthisiswhatcausesalunareclipse.Howolendoyouthinkalunareclipseoccurs?Explain.

LunareclipsescanonlyhappenwhenthemoonisfullanditpassesbehindEarthandintoitsshadow.Ifwehaveafullmoononceeverymonth,thenweshouldalsohavealunareclipseonceeverymonth.ThisthoughtmakessenseifyouthinkofEarth’sorbitandthemoon’sorbitsasbeinginthesameplane.However,themoon’sorbitisinclinedaboutfivedegreestoEarth’sorbit.Lookatthisimagecarefully.

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ThatmeansthatmostoftheCme,duringfullmoon,themoonpassesaboveorbelowEarth’sshadowandmissesitenCrely.Noeclipsetakesplace.Onlyonceortwiceayear,onaverage,doesthemoonpassthroughsomeporConofEarth’sshadow,causinganeclipsetooccur.ImagineyouareanastronautstandingonthemoonduringatotallunareclipseandwatchingEarth.Whatwouldyousee?

Ifduringafullmoon,thesun,theearth,andthemoonareallonebehindtheother,howdoesEarthnotblockthesun’slightfromreachingthemoon?

TypesofEclipsesWhenthemoonisinEarth’sshadow,nolightfromthesunreachesit,andthus,eventhoughitisintheposiConofafullmoon,itisnotilluminatedandcannotbeseen.BecausethemoonisinconstantmoConaroundEarth,itgraduallyenterstheshadowedarea—slowlydisappearingunClitcannotbeseenatall.Thenasitkeepsmoving,itgraduallyleavestheshadowedarea,enteringtheareawheresunlightcanreachitagain—slowlyreappearing.Thesechanges—frombrightnesstodarknessandbackagainintobrightness—cantakeuptofourhours.Sincethesunisalargelightsource,itcreatesshadowsthathavefullydarkareasandparCallydarkareas.Forthisreason,theshadowofEarthisactuallycomposedoftwoareas.Lookatthemodel.TheouterpartsoftheshadowaretheparCalshadow—areaswhereEarthblockspartbutnotallofthesun’srays.Incontrast,theinnerpartoftheshadowisacompleteshadowwhereEarthblocksalldirectsunlight.

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Lookatthemodel.InwhichposiConsisthemoon(A,B,C,D,E,F,orG)fullyshadowed?InwhichposiConorposiConsisitparCallyshadowed?Explain.

Therearethreetypesoflunareclipse:1. WhentheenCremoonisinthefullyshadowedarea,itisfullydarkened.Thisiscalledatotal

lunareclipse.2. Whenonlypartofthemoonisinthefullyshadowedarea,aparCallunareclipseoccurs—partof

themoonisdarkandtheotherpartisparCallyilluminated.3. WhenthemooniscompletelyintheparCallyshadowedarea,itissCllsomewhatlighted.Itis

difficulttonoCceanychangewiththenakedeye.Weneedprofessionaltelescopestoobservethechangesinthiskindofeclipse.

Followingarephotosofthemoonindifferenttypesofeclipses.Pleasewritebeneatheachonewhetheritisatotaleclipse,aparCaleclipse,ornoeclipse.AlsowritewhichposiConofthemooninthepreviousmodel(A,B.C,D,E,F,orG)fitseachphoto.

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WhyDoestheMoonTurnRedduringaTotalLunarEclipse?Averyspecialfeatureofthetotallunareclipseisthatalerthemoonhasgonedark,itturnsred.(YoumightwanttowatchaneclipsevideoandpayspecialaPenContothat.)ThereddishcolorisaresultofindirectlighCngofthemoon.WhilethemooniscompletelywithinEarth’sshadow,indirectsunlightsCllmanagestoreachandlightit.ThissunlightpassesthroughtheEarth’satmosphere.Then,itolenchangesdirecConbybouncingoffthegasmoleculesintheair.Someofthislightreachesthemoon.TheEarth’satmosphereactslikeafilter,absorbingmanycolors.Theremaininglightiscoloredreddish-orange.Itismuchdimmerthanoriginalwhitesunlight.Thislightreachesthemoonandmakesitappearred.TheexactcolorandbrightnessofthelightreachingthemoonduringaneclipsedependsonthehowmuchdustisinEarth’satmosphere.AleravolcanicerupCon,forexample,atotaleclipseisverydarkbecausethereisalotofvolcanicashinEarth’satmosphere.DuringthetotallunareclipseofDecember1992,themoonwasnearlyinvisiblebecauseofdustfromavolcanothateruptedinthePhilippines.Inthisreading,youlearnedwhatcausesalunareclipseandwhatkindsofeclipsesthereare.Yousawthatevenanamazingevent,suchasalunareclipse,canbeexplainedbyafewscienCficideasyoualreadyknow.Thisisanexampleofthepowerofscience.Asmallnumberofideascanexplainalargevarietyofphenomena!

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Reading11.4–DiffracAon

AdiffracCongraCngisaseriesofequallyspaced,microscopic,paralleldarklineswithatransparentareabetweenthem,somethinglikewhat’sshowninFigure1onlymuch,muchsmaller.WhenlightreachesadiffracCongraCng,itisabsorbedatthedarklinesandtransmiPedatthetransparentareas.Thus,whiletherewasaconCnuousareaoflightbeforethediffracCongraCng,alerittherearethousandsofindependentmicroscopicsourcesoflight.Fromthesemicroscopicsources,lightspreadsoutforwardinalldirecCons.SeeFigure2.ScienCstssaythatthelighthasbeendiffracted.

ThediffractedlighttravelsforwardandspreadsoutunClitreachedascreen.BecausethelightfromeachmicroscopicsourceonthediffracCongraCngtraveledforwardinalldirecCons,eachpointonthescreenisilluminatedbylightfrommany,ifnotall,ofthesourcesonthediffracCongraCng.UndercertaincondiCons,raysoflightcancanceleachotherout.Imagineanobjectbeingpulledonbothsidesbysprings.Ifthespringspullequally,theobjectwillnotmove,eventhougheachspringindependentlywouldhavemovedtheobject.Somethinglikethatcanhappenwithlight,eventhoughlightdefinitelydoesnotpushorpullthescreen.ThelightcomingfromthediffracCongraCngissetupsothatexceptforafewspots,thevariouscolorsoflightcancelthemselvesoutalmosteveryplaceonthescreen.ThatiswhyyougetseveralredspotsseparatedbyblanknesswhenyoushinearedlaserthroughadiffracCongraCng.Differentcolorsoflightwillremainintactatdifferentplacesonthescreen.Thuswhenyoushinewhitelight,whichisacombinaConofmanycolorsoflight,yougetareaswhereredlightremains(butnoothercolor),areaswheregreenremains(butnoothercolor),andsoon.Inthisway,youcanseeallthedifferentcolorsthatmadeupthewhitelight.

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Reading11.5–SolarEclipses

Ge`ngReadyIfyouthinkalunareclipseisanawesomeevent,asolareclipse(aneclipseofthesun)isevenmoreawesome.Inthemiddleoftheday,theskyslowlybecomesdarkasthesundisappears,leavingonlyahalooflightinthesky.AsolareclipseoccurswhenthemoonpassesbetweenthesunandEarthsothatthesunisallorpartlyblockedbythemoon.Somepeopleconsiderasolareclipsetobeoneofthemostamazingeventsinnature.Manypeopletravellongdistancestoobserveone.TheInternetisagoodsourceforphotosandvideosofsolareclipses.Accordingtowhatyoulearnedaboutphasesofthemoon,inwhichphasedoyouthinkasolareclipsecanoccur?Explainyourideas.Ifyouarenotsure,youmightwanttogobacktoReading10.2aboutphasesofthemoon.

AsolareclipsecanonlytakeplacewhenthemoonpassesbetweentheEarthandsun.Ifthemoon’sshadowhappenstofallsomewhereonEarth’ssurface,fromthatplacepeoplecanseesomepartofthesunbeingcoveredoreclipsedbythemoon.Asyoucanseeinthemodel,asolareclipsemaybeseenfromonlyasmallareaonEarth.Onlypeopleintheregionwherethemoon’sshadowfallswillbeabletoseeit.Whydoesthemoon’sshadownotcoverallofEarth?

ThereisevidencethatthemoonisveryslowlygeengfartherandfartherfromEarth.AssumingthedistancebetweenEarthandthesundoesnotchange,howwillthisaffectthesizeoftheshadowonEarthcausedbysolareclipses?Drawamodelofasolareclipsetohelpyouexplainyouranswer.YoumaywanttorecalltheinvesCgaConyoudidwithshadowsinLesson5.

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AsolareclipsemaybetotalorparCal,dependingonhowmuchofthesunisblocked.TwotofiveparCalsolareclipsesoccureachyearonEarth.Atotaleclipseoccursonlyonceeveryeighteenmonths.EachtotaleclipseisonlyvisiblefromaverysmallareaonEarth,wherethesunisinthefullshadowofthemoon.Therefore,itisraretoseeatotaleclipseatyourhouseoryourschool.Youwouldhavetowaitabout375yearstoseetwototalsolareclipsesfromthesameplaceonEarth.UsetheInternettofindoutwhenandwherethenexttotalsolareclipsewilloccur.Usewhatyoulearnedinthereadingaboutlunareclipsestoexplainwhythereisnotasolareclipseonceeverymonthwhenanewmoonphasetakesplace.Inthisphoto,youcanseeasolareclipseinwhichthesunappearsasaverybrightringsurroundingtheoutlineofthemoon.ManysolareclipseslooklikethisbecausesomeCmesthemoonlookstoosmalltoblocktheenCresun.ThereasonwhythemoonsomeCmesappearstoosmalltocoverthesunhastodowiththemoon’sorbitaroundEarth.Thatorbitisnotperfectlyroundbutisshapedlikeaslightoval.AsthemoonorbitsEarth,itsdistancefromtheearthvaries.SomeCmesthemoonisclosertoEarth,andsomeCmesitisaliPlefarther.Therefore,themoon’ssizeseemstovary.WhenitisfartherfromEarth,itlookssmaller.IfaneclipseoccursatthatCme,itistoosmalltocompletelycoverthesun,andyoucanseethebrightringofthesunbehindthemoon.However,ifaneclipseoccurswhilethemoonisclosertoEarth,themoonappearslargeenoughtocoverthewholesun.

SummaryUsethetabletocomparealunareclipseandsolareclipse..

Lunar Eclipse Solar Eclipse

What do we see from earth?

What phase is the moon?

Relative location of earth sun and moon

How much of the earth gets to see this eclipse?

Total or partial?

How often does this occur?

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Lesson12–InfraredLightandtheWaveModelLesson12.1–Whatisleavingaremotecontrol?


Whatwillwedo?Wewillexplorehowaremotecontrolworkstoexplorewhetherthereislightwecannotsee.

PredicAon:

Doyouthinkthataremotecontrolproduceslight?Explainwhyorwhynot.

Data

Action with remote Describe what happens when your teacher does the action with the remote

Points at you and presses the on/off button

Points at a TV or projector and presses the on/off button.

Points at a digital camera or a doc cam and presses the on/off button

Puts a piece of cardboard between the remote and the TV/projector when pressing button

Points the remote towards a mirror while pressing the button

Puts a piece of clear plastic or glass between the remote and the TV/projector

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Conclusion

1. Didyourresultssupporttheideathattheremoteisgivingofflight?Whyorwhynot?

2. Explainwhyyougotasimilarresultusingaremoteandusingaflashlight.(Hint:YoumaywanttoremembertheearlierlessonwhereyouusedvisiblelightinsteadofIR.)

3. Touseyourunderstandingevenmore,explaintosomeoneathomehowaremotecontrolworks.

4. Isanyofthelightfromtheremoteabsorbed?DesignaninvesCgaConyoucoulddotofigureouttheanswertothisquesCon.Describeordraw(orboth)howyouwouldtestwhetheranyIRlightisabsorbed.(Hint:LookbacktoLesson8toremindyourselfofhowyoudeterminedthatlightcouldbeabsorbed.)

5. MakeapredicCon.IftheremoteweregivingofflightandyoudidthedemonstraConyoudescribed,whatwouldyouexpecttohappen?Why?

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Reading12.2–InfraredLight

Ge`ngReadyYoudonothavetotouchafiretoknowitishot.Youcanseeitglowing,andyoucanfeelthatitishot.Haveyoueverfeltsomethingelsethatwashoteventhoughitwasnotglowingandyoudidnottouchit?ThinkofsomethingthatfitsthisdescripCon.Describewhattheobjectwasandhowcloseyouweretobeabletofeelthatitwashot.Asyouread,youwilllearnmoreaboutsomethingcalledinfraredlight.Infrared(IR)lightiswhyyouperceiveflamesashot!Bytheendofthisreading,youwillbeabletonameafewwaysthatpeopleusetheirunderstandingofinfraredlightoutsideofscienceclass.WhyArethereDifferentColorsofLightinaFlame?Acampfiregivesofflotsoflight.Whenyoulookatacampfire,mostoftheflameslookyellow.ButhaveyouevernoCcedthattherearedifferentcolorsinafire?Lookatthephotoofamatch.TheboPomoftheflameisblue,themiddleisreddish,andthetoplooksyellow.Inclass,youlearnedthatthewavelengthoflightdetermineswhatcoloryousee.Lightismadeofwaves,andthedistancebetweenanytwoconsecuCvewavesiscalledwavelength.Differentwavelengthsoflightcreatedifferentresponsesinyoureyes.Ifashortwavelengthofvisiblelightreachesyoureye,youreyerespondsbysendingacertainsignaltoyourbrain.Yourbrainreceivesthissignalandinterpretsitasblue.Ifalongwavelengthofvisiblelightreachesyoureye,youreyerespondsbysendingadifferentsignaltoyourbrain.Yourbraininterpretsthissignalasred.Iflighthasanevenlongerwavelengththanredlight,itdoesnotcreatearesponseinyoureye,becauseyoureyeisnotsensiCvetowavelengthsthatarelongerthanthoseofredlight.Becauseyoureyedoesnotrespondtothislight,itiscallednonvisiblelight.Nonvisiblelightwithawavelengththatislongerthanredlightiscalledinfraredlight.Whileacampfiregivesoffdifferentcolorsofvisiblelight,itgivesoffnonvisibleinfraredlight,too.Ofcourse,youcannotseeit!WhatMakesaFlameFeelHot?Eventhoughyoureyescannotdetecttheinfraredlightgivenoffbyafire,yourskincan.Wheninfraredlightreachesyourskin,yourskinabsorbsit.Thisabsorbedlightcausesthetemperatureofyourskintoincrease.Then,nervesinyourskinsendasignaltoyourbrainthatyourbraininterpretsashot.Acampfirecanfeelhotfrom10feetawaybecauseitgivesoffinfraredlightthatyourskindetects.SomeCmesobjectscangiveoffinfraredlightwithoutgivingoffanyvisiblelight.Astoveinyourhousemaylooknormaltoacamerathatdetectsonlyvisiblelight,butacamerathatdetectsinfraredlightcanshowadifferentpicture.Comparethesetwophotos.Thephotoonthelelwastakenwitharegularcamera.Youreyecannottellwhichburneronthestoveishotbecauseyoureyecannotseeinfraredlight.However,ifyouheldyourhandneareachburner,youcouldtellwhichonewashot,becauseyourskinwouldabsorbtheinfraredlightandsendasignaltoyourbrain.Thephotoontherightwastakenwithaninfraredcamera.Thecameraletsyoureyeseewhichburnerishot.HowDoesThisRelatetotheRemoteControlAcAvityWeDidinClass?Inclass,youusedaremotecontroltosendasignaltoatelevisionset.Then,youlookedattheremotecontrolwithadigitalcameraandsawsomethingflashingthatyoucouldnotseewithyoureyes.Howdidyourclassdeterminewhetherthesignalsentbytheremotecontrolwaslight?Explainwhythetestsyourclassdidhelpedyoudecidewhetherthesignalwaslight.

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Inclass,youdeterminedthatthesignalsentbyaremotecontrolwasakindoflightthatyoucannotsee.Younowknowthatthislightiscalledinfraredlight.Theinfraredlightofacampfire,amatch,andaburneronyourstovefeelshot.Whydoesitnotfeelhotwhenyoupointaremotecontrolatyourskin?Aremotecontrolgivesoffasmallamountofinfraredlight.Theamountissosmallthatitdoesnotheatyourskinenoughtosendasignaltoyourbrainthatitfeelshot.ButitisenoughlighttobedetectedbyaTV.HowDidPeopleNoAceInfraredLightintheFirstPlace?Youusedaremotecontroltostudyinfraredlightinclass,butthefirstpersontodiscoverinfraredlightdiditlongbeforeremotecontrolswereinvented.ThefirstpersontodiscoverinfraredlightwasSirFrederickWilliamHerschel.Heusedaprismtoseparatesunlightintoitscolors,justlikeyoudidinclasswithC-Spectra.Heknewthatlightcouldbeabsorbedbyobjectsandmakethemheatup.Hewantedtoknowwhethersomecolorsoflightheatedobjectsmorethanothers.ToinvesCgatethis,heplacedthermometerswithblackenedbulbsinthedifferentcolorsofthespectrumandrecordedtheirtemperature.Lookcloselyatthefollowingphotoofthermometers.Thereadingonthethermometersincreasesasyoulookfrombluetored.AlernoCcingthis,Herschelplacedathermometerjustoutsideoftheredpartofthespectrumwheretherewasnovisiblelight.Tohissurprise,hefoundthatthisareahadthehighestreadingofall!HerealizedthattheremustbesomekindoflightheaCngupthethermometerbutthathiseyescouldnotdetectit.Thislightwasinfraredlight.UsingwhatyouknowaboutcolorsandlightabsorpCon,explainwhySirFrederickWilliamHerschelusedthermometerswithblackenedbulbsinhisexperiment.

HowDoPeopleUseInfraredLight?Eventhoughyoucannotseeit,infraredlightisveryimportant.SinceHerscheldiscoveredthatsunlightcontainsinfraredlight,astronomershavebeenusingspecialIRcamerastolookatstarsandotherobjectsinthesky.Justasahotstovelooksdifferenttoaregularcamerathantoaninfraredcamera,objectsintheskylookdifferent,too.Thispictureshowsagalaxyphotographedwitharegularcamera(lel)andwithaninfraredcamera(right).Theinfraredcamerashowspartsofthegalaxythatareinvisibletotheeyebecausetheydonotgiveoffvisiblelight.SomeinfraredgogglesworkbydetecCngtheinfraredlightthatobjectsgiveoff.OtherIRgogglesuseaninfraredflashlighttobounceinfraredlightoffof

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objects.UsinganinfraredflashlightmakesobjectsappearbrightertosomeonewearingIRgoggles.IfsomeonewearingIRgogglesweretoshineaninfraredflashlightatyou,whatwouldyousee?Why?HowDoDoctorsUseInfraredLight?DoctorsalsouseinfraredlighttochecktheamountofoxygeninapaCent’sblood.Doctorsdiscoveredthatoxygen-richbloodabsorbsthemostinfraredlight,andittransmitsorscaPersvisibleredlight.Thatprobablymakessensetoyoubecauseitexplainswhyyourbloodappearsred!Ifbloodisnotoxygen-rich,ittransmitsmoreinfraredlightandlessvisibleredlight.ByshiningredandinfraredlightthroughapaCent’sfingerandmeasuringtheamountofeachtypeoflightthatcomesouttheotherside,doctorscandeterminehowmuchoxygenisintheblood.Knowinghowbloodabsorbs,transmits,orscaPerslightallowsdoctorstotestbloodwithouthavingtotakeabloodsamplefrompeople.Supposeyouwerewearingasensoronyourfinger,anditdetectedalotofinfraredlightandnotmuchvisibleredlight.Doesthismeanthatyourbloodhasalotofoxygeninit,oronlyaliPleoxygen?Why?

Inthisreading,youhavelearnedhowinfraredlightwasdiscoveredandyouhavelearnedaboutmanyusesforinfraredlight.Butinfraredlightisnottheonlykindoflightyoucannotsee.Inthenextlesson,youwilllearnaboutothertypesoflightthatyoucannotseeandhownonvisiblelightaffectsyourlifeeveryday.

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Lesson12.3–IntroducingtheWaveModel


Whatwillwedo?WewilldosomeacCviCestolearnmoreaboutthedifferencesbetweenvisibleandnonvisiblelight.Thenwewillreviseourmodeloflighttoaccountfornewevidence.

ProcedureAsyourteacherchangesthepitchcomingfromthecomputer,raiseyourhandwhenyoucannolongerhearthesound.Dideveryone’shandgoupatthesameCme?Why?

Aretheresoundsthatyoucannothear?Explain.

Describethewavemodelpresentedinclass.

Basedonyourunderstandingofthewavemodel,explainwhyyoureyecouldnotdetectthelightcomingfromtheremotebutthecameracould.

Conclusion

1. Accordingtothewavemodeloflight,whatmakesbluelightdifferentfromgreenlight?

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2. Compareredlightwiththeinfraredlightthatcomesfromtheremote.(Rememberthatcomparemeanstodescribewhatissimilarandwhatisdifferent.)

3. Describehowvisiblelightisdifferentfromnonvisiblelight.

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Lesson13–UltravioletLightandNonvisibleLightImageryLesson13.1–InvesAgaAngUVlight


Whatwillwedo?WewillinvesCgateanothertypeoflightthatoureyescannotdetect:ultravioletlight.

Data

SunscreensaredesignedtoprotectyourskinfromUVlight.Predictwhatyouwillgetintheexperiment,thenmakemeasurementsandcomparetheresultswithyourpredicCons.

1. IsthepercentofUVlightblockedbythesunscreengreaterorlessthanthepercentofvisiblelightblocked?Isthissimilartowhatyoupredicted?

2. WhywouldcompanieswanttheirsunscreentoabsorbnearlyalloftheUVlightthathitsitbutnoneofthevisiblelight?

3. Whatwouldsunscreenlooklikeifitabsorbedallofthevisiblelightthathitit?

Conclusion

1. Howdoesthesunscreenworksimilartothecolorfiltersthatyouhaveusedinpreviouslessons?

Ultralight(UV) light Visable Light

Reading without sunscreen

Prediction of how much light will be blocked by the sunscreen

Actual reading with the sunscreen

Actual percent of light blocked by sunscreen

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Reading13.2–Non-visiblelight

Ge`ngReadyImaginethatyourremotecontrolusedvisibleinsteadofnonvisiblelight.Wouldthisbeagoodidea?Why?

Today,youwillreadmoreaboutnonvisiblelight.Youprobablydonotrealizeit,butnonvisiblelightplaysanimportantroleinyourlifeeverysingleday!Bytheendofthisreading,youshouldbeabletodescribehowradios,cellphones,microwaveovens,orx-raysmachinesusenonvisiblelight.Byexplainingevenoneofthosetosomeonewhoisnotinyourclass,youcanhelpthemunderstandsomethinginteresCng.AndyouwillhelpyourselfunderstandnonvisiblelightevenbePerbyexplainingittosomeoneelse!HowDoesLightTravel?Inclass,youlearnedthatlighttravelsinasimilarwaytowavesmovingacrosswater.Yousawthatwhenwaterwavesmoveinapanofwater,theripplescanbespacedveryclosetogether(havingasmallwavelength)orveryfarapart(havingalargewavelength).Lightcanalsotravelwithawavelengththatisverysmallorverylarge.Butyoureyescanonlydetectlightifitswavelengthiswithinacertainrange.Humaneyescanonlydetectlightwithawavelengthbetween400and700nanometers.AnanometerisonebillionCmessmallerthanameter.Howsmallisthat?Asinglehaironyourheadisabout80,000nanometerswide.ThismeansthatthewavelengthofvisiblelightismorethanahundredCmessmallerthanthewidthofyourhair!Trytothinkaboutthisbeforeyoukeepreading.YoumayneedtoreadthroughthisdescripConagaintoreallyunderstandhowsmalltherangeoflightisthatyoureyecansee.Itisamazing!HowMuchNonvisibleLightIsThere?InfraredlighthasawavelengththatisaliPlegreaterthan700nanometers.Therefore,youcannotseeit.UltravioletlighthasawavelengththatisaliPlelessthan400nanometers.

Wavelength<400nanometers=nonvisible(UV)Wavelengthbetween400–700nanometers=visibleWavelength>700nanometers=nonvisible(IR)

Eventhoughthewavelengthsofinfraredandultravioletlightcanbeclosetothewavelengthsthatyoureyescandetect,youreyessCllcannotdetectthem.NonvisiblelightcanhaveawavelengthmillionsofCmessmallerthanahumanhairorbiggerthantheenCreEarth!Becausenonvisiblelightcanhavesomanydifferentwavelengths,scienCstscreatedasystemtokeeptrackofthem.Inthissystem,scienCstshavedividedallofthepossiblewavelengthsintocategories.Youhaveprobablyheardofsomeofthecategories,becausemanyofthedevicesyouuseeverydayoperateusingnonvisiblelight.Thelongestwavelengthsoflightarecalledradiowaves.Findthemonthefollowingchart.Theshortestwavelengthsarecalledgammawaves.Findthemonthechart.Inbetweenaremicrowaves,x-rays,infraredlight,ultravioletlight,andvisiblelight.

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Thereisalotoflightintheworld.Someofitisvisible.Someofitisnonvisible.Doyouthinkthatmostofthelightthathitsyoureyeislightthatyoucanseeornot?Explainyouranswer.(Thepreviouschartshouldhelpyou.)Althoughyoucannotseenonvisiblelight,yourbodycandetectitinotherways.Infraredlightmakesyoufeelwarm.Whenyougooutintothesunlight,yourskinabsorbsinfraredlight.Youcannotseethatlight,butyoucanfeelitaswarmth.Yourskinalsoabsorbsvisiblelightandultravioletlightwhenyouareinthesun.Inclass,youlearnedthattheultravioletlightfromthesuncangiveyousunburn.Eventhoughyoucannotseeit,nonvisiblelightfromthesunisveryimportantformakingEarthawarm,comfortableplacetolive.SomeWaysWeUseNonvisibleLightManyofthedevicesthatyouuseeverydayrelyonlightthatyoureyescannotdetect.Doyoueverlistentoaradio?Radiosaredesignedtodetectradiowaves.RadiowavesareatypeofnonvisiblewavegivenoffbyanantennaataradiostaCon.Justlikeyoureyedetectslightandsendsasignaltoyourbrain,aradioantennadetectsradiowavesandsendsasignaltoyourspeakers.Theradiospeakersthenproduceasoundthatyoucanhear.Radiowaveshavethelongestwavelengthofanykindoflight.Theirwavelengthcanbemanykilometerslong.Evenbeforereadingtoday,youprobablyknowsomethingaboutmicrowaves.Amicrowaveovenusesmicrowavelightwaves.Lookbackatthechartoftypesoflighttoseehowmicrowavelightcomparestoothertypes.Yearsago,scienCstsdiscoveredthatwatereasilyabsorbsmicrowavelight.Whenmicrowavesareabsorbedbywater,thetemperatureofthewaterincreases.Thisisusefultoknowbecausenearlyallofthefoodyoueathassomewaterinit.Whenyouputyourfoodinamicrowaveoven,thewaterinthatfoodabsorbsnonvisiblemicrowavelightandheatsup.Theheatedwaterthenheatsthefoodaroundit,whichmakesyourfoodhot.Lookatthisphoto.Whensomeonetakesfoodoutofthemicrowaveoven,thefoodishotbutthecontainerthefoodisinmaysCllbequitecool.WhydoyouthinkamicrowaveovencanheatfoodwithoutheaCngthebowl?Microwavesarealsousefulforsendingsignals.Hereissomethingyouprobablydidnotknow:Whenyoutalkonacellphone,yourphoneisactuallysendingandreceivingmicrowaves!UsingX-raystoSeethroughThingsWhilelongwavelengthsoflightareusefulforsendingsignalsoverlargedistances,shorterwavelengthsoflightareusefulforotherpurposes.X-raysandgammaraysmakeitpossibleforpeopletoseethroughthings.Haveyoueverbrokenabone?Ifso,adoctorprobablyusedanx-raymachinetotakeapictureofyourbones.Usinganx-raylightsource,doctorssendx-raysthroughyourbodytowardspecialphotographicfilmontheotherside.Whenx-raysstrikethefilm,theyareabsorbedandturnthefilmblack.Bonesshowupwhiteonanx-raybecausethesearetheareasofthefilmwhereveryfewx-raysareabsorbedbythefilm.Ifapersonwearsametalringwhiletheyhaveanx-ray,theringwillappearbrightwhite.Thephotoontherightshowsthis.Nowthatyouunderstandmoreaboutlight,absorpCon,andtransmission,youcanprobablyexplainthis.Doesmetalmostlytransmitorabsorbx-rays?Explainyouranswer.

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X-raysattheAirportX-raysareusefulforairportsecurityworkers,whocheckpassengers’luggagefordangerousmaterials.Byusingx-rays,theycanlookinsideluggagewithoutopeningit.Whenyouflyonaplane,workersshinex-raysonyourluggage.Thepicturetotherightshowswhattheysee.YoumaynoCcethattheobjectsinthispictureshowupasdifferentcolors.Anairportx-raymachineworksaliPledifferentlythanadoctor’sx-raymachine.Theobjectsdonotlooklikebones,dothey?Allx-rayshaveawavelengthofaboutasinglenanometer,buttheycanbealiPlebiggerorsmaller.Amedicalx-raymachineonlyusesonewavelengthofx-rays,butanairportmachineusesmanydifferentwavelengths.Sincedifferentmaterialsabsorbdifferentwavelengthsofx-rays,workerscantellwhatkindsofmaterialsareinsideofbags.Thishelpsthemtoknowwhethersomethingismadeofmetal,rubber,orcloth.Isthatnotamazing?Theyneverevenhavetoopenyourbagtoknowwhatisinside!However,x-rayscanbedamagingifapersonisexposedtothemtooolen.Medicalpeoplewearmetalapronsmadeoflead,ortheystandbehindaleadwallwhentheytakex-rays.Whywouldadark-coloredclothnotworkaswellaslead?Inthisunit,youhavelearnedalotaboutlight.Youlearnedthatlightmustenteryoureyeinorderforyoutosee.Youlearnedthattherearemanywavelengthsoflightthatyoureyecannotdetect.Eventhoughyoucannotseeit,youusenonvisiblelighteveryday.Itmakesyouwarm,helpsyoucommunicate,heatsyourfood,andcanevenhelpyouseethroughthings!

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Lesson13.3–HowwouldtheworldlookifpeoplecouldseeUVandIRlight?


Whatwillwedo?Wewillseehowtheworldmightlookifoureyescoulddetectnonvisibleultravioletorinfraredlight.

Conclusion

1. ImagestakenwithIRandUVcamerassomeCmesappearcolorful.HowdoyouknowthatthecolorinthesepicturesmusthavebeenaddedarCficially?

2. Basedonthepicturesyouhaveseeninclass,whymightUVandIRimagerybeusefulforastronomers?

3. WhymightUVandIRimagerybeusefulforfirefighters?

4. Duringapoweroutage,thelightsinacitycanallgoout.IfyouhadachoiceofusingeitheraUVorIRcameratohelpyousee,whichonewouldyouchoose?Explainyourchoice.

Documents

Can I Believe My Eyes?blogs.4j.lane.edu/macwilliam/files/2019/09/PS1-Barbs-Version-2019-20.pdfOpCcal illusions can be fun because they fool you. OpCcal illusions are a kind of trick