Chater 5: Relectio ad Reractio o Light Huge s Pricile: Proagatio o Waverots Ever oit o a waverot roduces wavelets. Radius o each wavelet is vt. New waverot is the surace taget to the wavelets. waverots Light Ras ad Geometric Otics sherical waverots ras Ater travelig ar become laar ras become arallel Whe sizes o aertures ad objects are large, we ca describe roagatio o light usig ras aloe. Ras travel i straight lie i a vacuum or trasaret medium. Ras ca be absorbed or scattered withi a medium. Ras ca be relected, reracted i a iterace o materials. The Laws o Relectio Agle o icidece, i = Agle o relectio, r The both ras ad the ormal at the oit o icidece lie i the same lae. The value o agle o icidece is o 40 icidet ra Normal i r relected ra A. 40 o B. 50 o C. 90 o D. oe o these. relectig surace How Do We See a Object? 1.Lumious source emits light ras..the object relects the light ( absorbs ad reemits). 3.The ras eter to our ees ad orm image i the retia. Plae mirror: object distace = image distace Thik, Aswer; Talk to our eighbors, Aswer Which is true? A. There is ol oe ra o light rom object to the ee as show i the sketch. B. Ol the ti o the object emits light. That light goes out i all directios. I drew 1 ra to kee the icture simle. C. All oits o the object emit light, i all directios. I drew 1 ra to kee it simle. 1
Thik, Aswer; Talk to our eighbors, Aswer Relectio vs Reractio Which ath takes the least time, rom P to Q? htts://uload.wikimedia.org/wikiedia/comm os/a/ac/agle_o_icidece_reractio_exa mle.jg Disersio i a Prism The Reractio o Light: Sell s Law Light travels with dieret seeds i dieret media because wavelegth chages but reuec remais same. seed o light medium1 c i vacuum. Reractive idex, 1 1 v c seed o light 1 or, v i medium. Red light has logest wavelegth. Thereore, smallest idex o reractio. Hece, the red color beds least. c c v Mirages: medium Sell s Law: 1 si 1 si Problem: A laser beam eters a glass slab b makig a agle 3o with the glass surace. What is the beam s directio o the other side o the glass? Assume, g = 1.5. suerior Total Iteral Relectio Alicatios o Total Iteral Relectio 1 90O c c Otical ibers edoscoe 1 The critical agle is oud b usig Sell s law: si c 1 si 90o si c 1 c si 1 1 Problem: What is the critical agle or a diamod. Reractive idex o the diamod is.417. rai sesig wier
Polarizatio b Relectio Light is totall olarized whe the relected ra ad the trasmitted ra are eredicular. Brewster s agle is the agle o icidece or which the relected light is comletel olarized. si si i i t t i sib t si 90 B t t cosb tab i Fish aear to be at little higher tha it actuall is because o reractio. Image Formatio b Reractio Problem: A deect i a diamod aears to be.00 mm below the surace whe viewed rom directl above that surace. How ar beeath the surace is the deect. Air =1.00 Surace Diamod 1 =.419 1 1 Actual locatio o deect =1.00 1 =.419 1 1 1 Actual locatio o deect As log as ou are directl above the deect ad its image, the agles 1 ad are earl 0. Sice cos0 = 1, 1 s The agles 1 ad are related b Sell s Law: 1 1 si si 1 The actual deth o the deect is ad it aears to be at a deth o. These uatities are related b: s s ta ad ta1 1 or, ta ta Dividig (1) b () gives: 1 cos1 cos =1.00 1 =.419 1 1 Actual locatio o deect 1 aaret deth real deth (geeral result) The actual deth o the deect i the diamod is the 1.419.00 mm 4.84 mm. 1.00 1 1 3
Thik, Aswer; Talk to our eighbors, Aswer A ra o light asses thru a sheet o glass which is thick at the bottom ad thi at the to. Which wa is the ra travelig ater it has assed through the glass Reractio i Prism ad Thi Leses Prism A: bet toward the thi ed B: udeviated C: bet toward the thick ed Les Ra Tracig: covergig les Thik, Aswer; Talk to our eighbors, Aswer Lumious object Focus Focus The object distace is related to the image distace b Shar image, o scree I ou move the scree towards the les, the image: A) remais the same B) gets a bit dimmer C) becomes uzzier. D) becomes uright E) disaears Ra Tracig: covergig les Ra Tracig: divergig les Object is withi the ocal legth. Image is virtual. 4
Thik, Aswer; Talk to our eighbors, Aswer Thik, Aswer; Talk to our eighbors, Aswer Light eters a covergig les, show as a sigle red ra. Which ra cotiues the red ra? Which ra cotiues the red ra? A C B D E) Noe o these, or ot eough io! Sig Covetio image height magiicatio, m object height h image distace object distace h Problem : (a) For a covergig les with ocal legth o 3.50 cm, id the object distace that will result i a iverted image with a image distace o 5.00 cm. Use a ra diagram to veri our calculatio. (b) Is the image real or virtual? (c) What is the magiicatio? (a) 3.50 cm 5.00 cm? 1 1 0.0857 cm 3.50cm 5.00cm so, 11.7 cm (c) m - because image is iverted. Problem : Whe a object is laced 6.0 cm i rot o covergig les, a virtual image is ormed 9.0 cm rom the les. What is the ocal legth o the les? 1 Image b covex mirror Pricial ras used to locate Image The image is uright, virtual, smaller tha the object, ad closer to the mirror tha the object. 1. A ra arallel to the ricial axis is relected as i it came rom the ocal oit. (gree). A ra alog a radius is relected back uo itsel. (red) 3. A ra directed toward the ocal oit is relected arallel to the ricial axis. (blue) 5
Covex mirror rovides larger ield o view Plae mirror Cocave mirror A cocave (or covergig) mirror curves toward the observer. Covex mirror That is wh a covex mirror is laced i the asseger side o a car. Pricial ras used to locate Image Cocave mirror rovides detailed view 1. A ra arallel to the ricial axis is relected through the ocal oit. (gree). A ra alog a radius is relected back uo itsel. (red) 3. A ra alog the directio rom the ocal oit to the mirror is relected arallel to the ricial axis. (blue) Whe object is i betwee ocus ad mirror, image is magiied. Mirror euatio Mirror euatio is same as les euatio. Problem : A object.00 cm high is laced 1.0 cm i rot o a covex mirror with a radius o curvature o 8.00 cm. Where is the image ormed? where = 1.0 cm, = 0.5R = 4.00 cm, ad is the ukow image distace. Solvig gives = 3.00 cm. The image is behid the mirror. 6