OPTICS. (b) 3 3. (d) (c) , A small piece

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1 AQB-07-P If the refrctive indices of crown glss for red, yellow nd violet colours re , nd respectively nd for flint glss re 1.644, nd respectively, then the dispersive power for crown nd flint glss re respectively () 0.04 nd nd nd (d) 0.04 nd The ngulr position of first diffrction minimum due to single slit diffrction is for light of wvelength 5000Å. If the width of the slit is cm, then the vlue of 0 is () (d) The ngles of prism re 0 0, 60 0 nd Wht is the refrctive index of liquid to be kept in contct with the longest fce so tht ry normlly incident on the smllest fce gets just internlly reflected t the longest fce? (Given refrctive index of glss of prism is 1.5) () 4 4 (d) Two sphericl mirrors-one convex nd the other concve re of the sme rdius r. They re rrnged co-xilly t distnce r from ech other. A smll circle of rdius is drwn on the convex mirror ner the pole. The rdii of the first two imges re r (), 41,, (d), 645. A hollow sphere of glss hs its internl rdius cm nd its externl rdius cm nd is filled with wter 4. A smll piece of metl rests t the lowest point of the wter nd is viewed by n eye situted verticlly bove the centre of the sphere. The mgnifiction is () (d) 6 C 646. A person with defective eye hs his fr point t infinity. But his ner point is t 50 cm from the eye. The lens to be used to bring the ner point to 5 cm is () concve lens of power D convex lens of power + D concve lens of power 0.5 D (d) convex lens of power 0.5 D

2 AQB-07-P A smll fish 0.4 m below the surfce of lke is viewed through simple converging lens of focl length m. The lens is kept 0. m bove the wter surfce such tht the fish lies on the opticl xis of the lens. (Given the refrctive index of wter is 4/). The imge of the fish will be t distnce () 60 cm from the lens on the sme side s the fish 40 cm from the lens on the sme side s the fish 0 cm from the lens but on the other side of lens (i.e. not on the sme side of fish) (d) infinity 648. A simple two-lens telescope hs n objective of focl length 50 cm nd n eye-piece of focl length.5 cm. The telescope is pointed t n object t very lrge distnce which subtends n ngle of 1 milli rdin on the nked eye. The eye-piece is djusted so tht the finl virtul imge is formed t infinity. The size of the rel imge formed by the objective is () 5 mm 1 mm 0.5 mm (d) 0.1 mm 649. Dimeter of plno-convex lens ADBEA is 6 cm nd thickness t the centre is ED= mm. The speed of light in the mteril of the lens is 10 8 m/s. Then the focl length of the lens is (neglect the term (ED) being smll A E D () 15 cm 0 cm 0 cm (d) 10 cm B 650. The plne surfce of plno-convex lens is silvered nd it then cts like concve mirror of 0 cm focl length. If for lens is 1.5, the rdius of curvture of the convex surfce is () 15 cm 0 cm 60 cm (d) 90 cm 651. If Young s experiment is performed using two seprte identicl sources of light insted of using two nd one single source, then () the interference fringes will be brighter the interference fringes will be drker no fringes will obtined (d) the distnce between bright nd drk fringes increses 65. A thin prism P 1 of ngle 4 0 nd mde from glss of refrctive index 1.54 is combined with nother thin prism P mde from glss of refrctive index 1.7 so tht ry undergoes no devition. The ngle of prism P is () (d) A prism (=1.5) hs refrctive ngle of 0 0. The devition of monochromtic ry incident normlly on its one surfce will be (sin = 0.75) () (d) A ry of light psses from vcuum into medium of refrctive index, the ngle of incidence is found to be twice the ngle of refrction. Then the ngel of incidence is

3 AQB-07-P-108 () cos 1 / cos 1 / 1 sin (d) sin 1 / 655. The plne fce of plno-convex lens is silvered. If be the refrctive index nd R, the rdius of curvture of curved surfce, then the system will behve like concve mirror of rdius of curvture () R R/( 1) R / (d) {(+1)/( 1)}R 656. As shown in the figure, bem of light, converging towrds O, is incident on convex mirror of rdius of curvture 60cm. If PO = 50 cm, imge will be P O () rel, enlrged nd t distnce 75 cm from P in front in front of the mirror s virtul, diminished nd t distnce 70 cm from P behind the mirror rel, diminished nd t distnce 70cm from P in front of the mirror (d) virtul, enlrged nd t distnce 75 cm from P behind the mirror 657. Two plne mirrors X nd Y re kept prllel to ech other t seprtion 5 cm, s shown. A ry of light is incident on the mirror Y t n ngle 60 0 t its end/edge. Length of ech mirror being 10 m, number of times the ry is reflected, including the initil one, before it emerges is x 5cm 60 0 y 10 m () (d) Refrctive index of ir being , thickness of ir column tht will hve one more wvelength of blue light (4000 Å) thn in equl thickness of vcuum is () 1.4 m 0.8 m 0.4 m (d). m A continer hs perfectly reflecting plne bottom. It is filled with wter to depth 0 cm. An object is kept t height 15 cm bove the surfce of wter. Distnce of the finl imge from wter surfce is () 50 cm 60 cm 5 cm (d) 45 cm 660. A prllel bem of light, consisting of four colours(a, B, C nd D), is incident the mteril of prism for the A+B+C+D colours A, B, C nd D hs the vlues, A = 1.1, 0 0 B = 1.19, C = 1.14, D = Which colour will be seprted by the prism from the others? () A B C (d) D 661. Refrctive indices of crown glss for violet nd red colours re, respectively, 1.5 nd 1.48 nd those of flint glss re 1.77 nd 1.7 respectively. A prism of ngle 9 0 is mde of crown glss nd white light is incident on this prism t smll ngle. Another flint glss prism is combined with the crown glss prism so tht there is no devition of incident light. Net dispersion of the combined system is

4 AQB-07-P-109 () (d) A qurter cylinder of rdius R nd mde of glss of refrctive index 1.4 is kept on tble. A point object O is plced t distnce mr from it s shown. Determine m so tht ry from P emerges prllel to the tble 5 () O mr (d) 66. Two plno-concve lenses mde of glss of refrctive index hve rdii of curvture of their curved surfces s 0 cm nd 40 cm. They re kept in contct with their curved surfces fcing ech other s shown in the figure. The spce between them is filled with wter 4. System behves s () convergent lens of focl length 75 cm divergent lens of focl length 80 cm convergent lens of focl length 40 cm (d) divergent lens of focl length 75 cm glss glss 664. A convex lens of focl length 50 cm nd concve lens of focl length 10 cm re plced with their optic centres on the sme xis nd with distnce d between them. For wht vlue of d will prllel bem of light incident on the convex lens leve the concve lens s prllel bem? () 50 cm 10 cm 0 cm (d) 40 cm 665. Mgnifying power of n Astronomicl Telescope for distnt objects is 8. If the objective nd the eye lens re t seprtion 45 cm nd the finl imge is formed t infinity, focl lengths of objective nd the eye lens re () 40 cm, 5 cm 0 cm,.75 cm 6 cm, 4.5 cm (d) 5 cm, 10 cm 666. Dispersive powers of the mterils of two lenses A nd B re in the rtio 5 : 4. If the chromtic combintion of these two lenses plced in contct is convergent lens of focl lengths of lenses A nd B, respectively re () 0 cm, 0 cm 0 cm, 0 cm 15 cm, 1 cm (d) 40 cm, 10 cm 667. A lens of unknown nture (convex/concve) nd of focl length 0 cm forms n erect imge 4 times the size of n object. Determine the nture of lens nd lso the distnce of object from the lens. () convex, 15 cm convex, 40 cm concve, 15 cm (d) concve, 40 cm 668. A lens mde of mteril of refrctive index / when plced in ir behves s shown in the figure (i) nd when plced in surrounding of refrctive index s, it behves s shown in figure (ii), s is

5 AQB-07-P-0 ir ir s s 10cm 0cm () (d) A 100 W bulb is hnging t height of 4m bove the centre of tble 6m 6m. Rtio of intensities of illumintion t the centre of ny edge nd t ny corner is () : In Young s double slit experiment, light consisting of two wvelengths 7000Å nd 6000Å is used to obtin interference fringes. If the distnce between the two slits is 1 mm nd the distnce between the plne slits nd screen is 100cm, wht is the minimum distnce from centrl mximum where bright fringes due to both the wvelength coincide? () 0.54 cm 0.6 cm 0.4 cm (d) 0.8 cm (d) In young s interference experiment with light of wvelength 6000 Å, one of the slits is covered by thin glss plte of refrctive index 1.5 while the other slits is coved by nother glss plte of sme thickness but of refrctive index 1.75 O is point on the screen where the centrl mximum fell before inserting the glss pltes, its intensity being I 0. It is found tht wht used to be the fifth mximum erlier, now flls t O. Assuming negligible bsorption of light by the glss pltes, find the thickness of glss pltes nd lso the intensity t O (fter the glss pltes re inserted) () cm, I cm, I0 I cm, (d) I 0 cm, 67. In single slit Fruhofer diffrction with light of wvelength 5000 Å, distnce between the first nd the fourth minim in the diffrction pttern formed on the screen is 4.5 mm. Wht is the distnce between the first drk fringes on ech side of the centrl mximum? () 4.5 mm.5 mm.0 mm (d).0 mm 67. In Frunhofer diffrction pttern obtined with single slit, phse different between secondry wvelets from the ends of the slit, t the position of first secondry minimum is () / (d) / A nd B re two polrisers hving their trnsmission xes perpendiculr to ech other. Another polrizer C is plced between the two such tht when unpolrised light of intensity I 0 I 0 flls on A, the intensity of light tht emerges from B is. Angle between the trnsmission xes of A nd C () (d) 15 0

6 AQB-07-P In certin double slit experimentl rrngement, interference fringes of width 1.0 mm ech re observed when light of wvelength 5000 Å is used. Keeping the set up unltered if the source is replced by nother of wvelength 6000Å, the fringe width will be () 0.5 mm 1.00 mm 1. mm (d) 1.5 mm 676. In the Young s doubles slits experiment, if the phse of ech light wve coming from the two slits is chnged by, the fringe pttern will () remin unchnged shift downwrds by hlf fringe width dispper (d) shift upwrds by hlf fringe width 677. A smll mirror of re A nd mss m is suspended in verticl plne by mens of weightless thred. A bem of light intensity I flls normlly on the mirror nd the string is deflected by smll ngle. If the mirror is perfectly reflecting then is IA () mgc IA c mgc IA (d) zero 678. Two coherent sources of different intensities send wves which interfere. The rtio of mximum intensity to the minimum intensity is 5. The intensities of the sources re in the rtio () 5 : 1 5 : 1 9 : 4 (d) 65 : 1 d S 1 B S =0 0 Q O P 679. A lens is plced between source of light nd wll. It forms imges of re A 1 nd A on the wll for its two different position. The re of the source of light is A A () 1 A 1 A 1 1 A 1 A 1 (d) 1 A A 680. In the figure given below there re two convex lens L 1 nd L hving focl lengths F 1 nd F respectively. The distnce between L 1 nd L will be () F 1 F F 1 + F (d) F 1 F L 1 L