FORMULABOOKLETPHYSICSCLASS12
CHAPTERRAYOPTICS


PhysicsFormulas
Ray Optics
Inoptics,therayisageometriclightmodelobtainedbyselectingaraisedcurvein thewavefrontofactuallightthatindicateswheretheenergyisflowing.Raysare usedtomodellightpropagationthroughthevisualoropticalsystembydividing thefieldofreallightintodirectraysthatarenottransmittedthroughasystemwith raytracingtechniques.Thisallowsevenmorecomplexopticalsystemstobe analyzedorsimulatedbycomputer
RaytracingusesMaxwell'sequation,whichisvalidaslongasthelightwavesare wavesthatpropagatearoundobjectsthataremuchlargerthanthelight wavelength Rayopticsorgeometricalopticsdonotdefinedi ractionevents, whichrequirewaveOpticstheory Otherwaveeventssuchasinterferencecanbe modeledinmoderateconditionsbyaddingaphasetotheraymodel
Definition
Thelightrayisalinestraighttothefrontlightwaves;itstangentiscollinearwith thevectorofwaves Lightraysinhomogeneousmediaarestraightforward They bendattheinterfacebetweentwodi erentmediaandmayturnatthepointwhere therefractiveindexchanges Geometricopticsdescribeshowradiationis transmittedthroughthevisualsystem Theobjectstobeimagedareconsideredas collectionsofindependentpointsources,eachofwhichproducescircularfront wavesandcorrespondingexternalrays Radiationfromeachareacanbe transmittedmathematicallytoobtainacorrespondingpointintheimage
HowtoMakeanimageWithaLens?
Therealimageofthebodyplacedbetween2fandffromtheconvexlenscanbe capturedonascreenplacedintheimageareaevenifthescreenisremoved The screenseparatesraysfromanobjectintoanimageintheskyandthendeviates Lasershowprojectionisanexcellentexampleofthis
WhatarethefeaturesofWhitelight?
Imageformationrequiresregularrefraction/reflection Radiationgeneratedinone locationisexpectedtoreachthesameimagelocation That’swhycertainthings likeabookpagedon’tproduceanimage
Whataretheusesofthelens?
Inthecaseofmyopia,theimageisfocusedonaretinathatcanberepairedwith thehelpofadefectivelens Inthecaseofhypermetropia,theimagefocusesonthe othersideoftheretina,whichcanbecorrectedwiththehelpofaflexiblelens A typeofcylindricallensisusedtocorrectastigmatism
Totalintervalrefraction

Criticalangle,


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Len'smakerformula
FromSnell’sLaw
i=angleofincidence r=angleofrefraction d=i–r=angleofdeviation









Denser→rarermedium
Lightbendsawayfromnormal(d=r i) Rarer→densermedium
Lightbendstowardsnormal(d=i-r) μ =refractiveindexof2mediumwrt1 μ =refractiveindexof2medium
Norefraction iflightisincidentnormallyonboundary refractiveindexof1 medium=refractiveindexof2medium
Whenlightrayundergoesrefraction,thereisachangeinitsvelocityand wavelengthbutfrequencyofthelightdoesnotchange V –velocityoflightin1medium V –velocityoflightin2medium λ wavelengthoflightin1medium λ wavelengthoflightin2medium
RealandApparentDepths
Duetorefraction,depthofanopticallydensermediumappearstobelessthanits realdepth
Criticalangle
