nr 2 nr 4 Correct Answer 1 Explanation If mirror is rotated by anglethan beeping incident ray fixed, reflected ray rotates by 2 Option 4

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1 Q. No. A small plane mirror is placed at the centero a spherical screen o radius R. A beam o light is alling on the mirror. I the mirror makes n revolution per second, the speed o light on the screen ater relection rom the mirror will be nr nr nr nr Correct Answer I mirror is rotated by anglethan beeping incident ray ixed, relected ray rotates by. So, speed o mirror nr Hence speed o relected light = nr Q. No. Which o the ollowing is not true about the image ormed by convex mirror? It is erect It is virtual It is diminished It lies beyond ocus Correct Answer Image is always eect, virtual and diminished so orms behind mirror. Q. No. For a real object, a convex mirror always orms an image which is Real and inverted Virtual and inverted Virtual and erect Real and magniied Correct Answer Virtual and erect Q. No. The image o a bright object is brought on the screen with a concave mirror. I upper hal o mirror is covered, what is the eect on the image? Its size is halved Brightness is reduced Image changes position Image disappears Correct Answer As rest o the mirror orms the sequred imagewith reduced intensity. Q. No. 5 A convex mirror is used to orm an image o a real object. Then tick the wrong statement The image lies between the pole and ocus The image is diminished in size The image is erect The image is real Correct Answer As image ormed is always virtual

2 Q. No. 6 A concave mirror is used to orm an image o the sun on a white screen. I the lower hal on the mirror were covered with an opaque card, the eect on the image on the screen would be To make the image less bright than beore To make the lower hal o the image disappear To prevent image rom being ocused None o these Correct Answer As rest o the mirror orms the sequred imagewith reduced intensity. Q. No. 7 In a concave mirror an object is placed at a distance x rom the ocus and the image is ormed at a distance x rom the ocus. Then the ocal length o the mirror is x x x x x + x Correct Answer v u v+u = vu u + x v x x + x v v u uv = u+v +x +x = +x +x + x +x = + x +x +x x = x +x Q. No. The image ormed by a convex mirror o ocal length 0 cm is one quarter o the size o object. The distance o object orm the mirror is 0 cm 0 cm 90 cm 60 cm Correct Answer u u m= v= v v v u u v v 0 u=90cm

3 Q. No. 9 A convex mirror has ocal length. A real object is placed at a distance in ront the pole, produces an image at Ininity Correct Answer v u =+ v v= Q. No. 0 A concave mirror o ocal length produces an image n times the size o the object. I the image is real then the distance o the object rom the mirror, is n n n n+ n n+ Correct Answer m= v = n u v u n+ u= n v=nu nu u Q. No. A convex mirror o ocal length produces an image (/n)th o the size o the object. The distance o the object rom the mirror is n n n+ n Correct Answer m= v = u n v u u= n u v= n n u u

4 Q. No. What is the magniication when the object is placed at a distance o orm the pole o a convex mirror? Correct Answer u = t, v =?, = + + v + v m= = = u + v= Q. No. A short linear object o length L lies on the axis o a spherical mirror o ocal length at a distance u rom the mirror. Its image has an axial length L equal to / L u / u+ L / u L L u Correct Answer v u dv du + =0 dt v dt v dv v v = dv= du du u u L = L v u

5 Now v u u = v u So v L = L u v L = L u u u v Q. No. The reractive index o water with respect to air is and the reractive index o glass 9 9 Correct Answer aw gw = = = a g 9 with respect to air is. The reractive index o water with respect to glass is g w = 9 Q. No. 5 Air has reractive index.000. The thickness o air column, which will have one more 0 wavelength o yellow light 6000 A than in same thickness o vacuum, is mm cm m km Correct Answer a =.000, vac =.000 optical path in other medium t Acc. to given condition t So no. o wavelength in t thickness = air So no. in other medium = t air t t So, air air

6 t A.000 t A So,t=0 m =mm Q. No. 6 A glass slab o thickness cm contain, the same number o waves as 0 cm o water when both are traversed by the same monochromic light. I the reractive index o water is, the reractive index o glass is Correct Answer optical path o glass = g t g optical path o water= t w w noowaves= t Since both contain same no. o waves g tg w tw So = cm= 0cm g 5 = g Q. No. 7 A beam o monochromatic blue light o wavelength 0 nm in air travels in water =. Its wavelength in water will be 0 nm 560 nm 5 nm 00 nm Correct Answer h 0 nm = = = nm 5

7 Q. No. I velocity o light in a certain medium is.50 m/s, or the medium would be.5 Correct Answer C = = v Q. No. 9 The wavelength o sodium light is 59 nm in air. What will be the wavelength o sodium light it is travels in glass o reractive index.5? 59 nm 59.5nm 59 nm.5 None o these Correct Answer h 59 nm = =.5 Q. No. 0 Light travels with a speed o 0 m/s in crown glass o reractive index.5. What is the speed o light in dense glass o reractive index.?.0 m/s.670 m/s.00 m/s.00 m/s Correct Answer v M = v. 0 =.5 v v =.67 0 m/s Q. No. I the reractive index o water is and that o glass slab is 5, then the circle angle o incidence or which a light tending to go rom glass to water is sin sin 5 sin sin 5 Correct Answer

8 sin = M sin c c = M M sin = c 5 c=sin 5 Q. No. I the critical angle or total internal relection rom a medium to vacuum is 0 0, the velocity o light in the medium is 0 m/sec.50 m/sec 60 m/sec 0 m/sec Correct Answer sin c = n= = 0 n sin0 n= e So n= v=.50 m/s v Q. No. The critical angle or a medium is Then reractive index o the medium will be Correct Answer sin c = n n= Q. No. A ray o light enters rom a denser medium into rarer medium. The speed o light in the rarer medium is twice that in denser medium. What is the critical angle or total internal relection to take place None o these Correct Answer v U r D = = v v D D

9 r D = sin = c c =0 r D 0 sin c = Q. No. 5 The reractive index o water is and that o glass is5. What will be the critical angle or the ray o light entering water rom the glass sin 5 5 sin sin sin Correct Answer n sin c = n sin = c 5 c sin = 5 Q. No. 6 A ish is a little away below the surace o a lake. I the critical angle is 9 0, then the ish could see things above the water surace within an angular ring o 0 where =9 =90 =9 = 0 Correct Answer 0 0 0

10 0 0 = 9 =9 Q. No. 7 A ish rising vertically with speed m/s to the surace o water sees a bird diving vertically towards it with speed 9 m/s. Given aw =. The actual velocity o dive o bird is 6 m/s m/s. m/s.5 m/s Correct Answer Re. vel. o bird wrt. Fish = 9 m/s So act. Vel. o bird which ish sees = 9 m/s m/s At rest = 6 m/s nr x b/ app = xblactual n i v b/ app = v blactual v b/ actual = 6m/s v =.5m/s b/ actual Q. No. A vessel is hal illed with a liquid o reractive index. The other hal o the vessel is illed with an immisicibel liquid o reractive index.5.the apparent depth o the vessel is 50%o the actual depth. Then is Correct Answer d d A = d d B =.5 d d A +d B = d d 5 = =.67

11 Q. No. 9 An air bubble in glass slab =.5 rom one side is 6 cm and rom other side is cm. The thickness o glass slab is 0 cm 6.67 cm 5 cm None o these Correct Answer d d A(apparent) d nr = d ni =(.5)(6cm) A(actual) =9cm A(actual) = (.5)(cm) B(actual) =6cm d A +d B =5cm Q. No. 0 I in a plano convex lens, radius o curvature o convex surace is 0 cm and the ocal length o the lens is 0 cm, the reractive index o the material o the lens will be Correct Answer = R R = =. Q. No. A double convex lens o ocal length 6 cm is made o glass o reractive index.5. The radius o curvature o one surace is double that o other surace. The value o large radius o curvature is 6 cm.5 cm 9 cm cm Correct Answer = R R = R R R=9cm

12 Q. No. A lens behaves as a converging lens in air and a diverging lens in water. The reractive index o the material is Equal to unity Equal to. Between unity and. Greater than. Correct Answer air =, water=. So < <. rms Q. No. A double convex lens made o material o reractive index.5 and having a ocal length o 0 cm is immersed in a liquid o reractive index.0. The lens will behave as Converging lens o ocal length 0 cm Diverging lens o ocal length 0 cm Converging lens o ocal length 0/ cm Converging lens o ocal length 0 cm Correct Answer nl = ns R R.5 =.() R R.5 =.() R R i ii = 0 cm So diverging lens Q. No. A convergent lens o ocal length 0 cm and made o a material with reractive index. is immersed in water. The lens will behave as a Converging lens o ocal length 0 cm Converging lens o ocal length less than 0 cm Converging lens o ocal length more than 0 cm Divergent lens. Correct Answer nl = ns R R.5 = R R.().5 =.() R R i ii = 0 cm So diverging lens

13 Q. No. 5 A double convex air bubble in water will behave as Convergent lens Divergent lens Plane glass slab Concave mirror Correct Answer Air is rarer medium than glass so air bubble in glass behave as diverging lens. Q. No. 6 A glass concave lens is placed in a liquid in which it behave like a convergent lens. I the reractive indices o glass and liquid with respect to air are a g and a l respectively, then = 5 a g > a g < a g a l a l a l = a g a l Correct Answer For a concave lens to behave as convergent lens < lens So < surrounding a g a l Q. No. 7 A thin convergent glass lens g =.5 has a power o +5.0 D. When this lens is immersed in a liquid o reractive index l it acts as a divergence lens o ocal length 00 cm. The value o l must be Correct Answer P = +5.0 D, = = 00 =0 cm P 5 = R R = lens.() 0 R R lens =.() 00 e R R i ii 5 =.5

14 5 +0 = 5 = 5 9 Q. No. A lens with power +P is immersed in water. Its power Increases Decreases Remains unchanged Increases or red color, decreases or blue Correct Answer Converging lens becomes less converging so P decreases Q. No. 9 The distance between the object and real image ormed by a convex lens is D. i the magniication is M, then ocal length is M D (M ) M D (M+) M D M M D M+ Correct Answer v D D u+v = D, + M = u u u D u =.() M+ = v u D v and Since u = M = + M u MD So v =.() +M +M +M = = v u MD D MD = M+ Q. No. 0 Magniication produced by a concave lens cannot be More than one Equal to one Less than one Equal to or less than one Correct Answer More than one

15 Q. No. A lens orms a sharp image on a screen. On inserting a parallel sided glass slab between the lens and the screen, it is ound necessary to move the screen a distance d away rom the lens in order or the image to be sharp again. I the reractive index o the glass relative to air is, then the thickness o the slab is d d/ d d Correct Answer Due to intersection o slab, image shit by Shit = t So d = t d t = Q. No. A convex lens o ocal length is put in contact with a concave lens o same ocal length. The ocal length o combination is Zero F Ininity Correct Answer P eq = P +P =+P P=0 So = Q. No. Two thin lenses o ocal lengths 0 cm and 5 cm are placed in contact. The power o the combination is 0.5 D 9 D 5 D.5 D Correct Answer P eq = P +P P =,P =,P eq =+9D 0.0m 0.5m

16 Q. No. A concave and convex lens have same ocal length o 0 cm and are put in contact. The combination is used to view an object o 5 cm length kept at 0 cm rom the lens combination. As compared to object, the image will be Magniied and inverted Diminished and erect O same size and erect O same size and inverted Correct Answer Since P eq = 0, So net eect is zero, Hence, image is same size and erect Q. No. 5 Two thin lenses o ocal lengths and are placed in contact. The ocal length o the complete lens is Correct Answer = + eq eq = + Q. No. 6 Parallel rays o light are ocused by a thin convex lens. A thin concave lens o same ocal length is then joined to the convex lens and the result is that The ocal point shits away rom the lens by a small distance The ocal point shits towards the lens by a small distance The ocal point does not shit at all The ocal point shits to ininity Correct Answer Net power become zero Q. No. 7 The lenses o power + and diopters are placed in contact. What will be the ocal length o the combination 0 cm.5 cm 6.6 cm. cm Correct Answer P eq = + D D = +0 D eq = =0 cm Peq eq =0 cm

17 Q. No. For a normal eye, the least distance vision is nearly 0 cm 5 cm 50 cm 00 cm Correct Answer 5 cm Q. No. 9 In a simple microscope, the distance o object rom the lens should be More than the ocal length o lens Less than the ocal length o lens More than twice the ocal length More than ocal length but less than twice the ocal length Correct Answer To orm virtual image object should be between ocus and optical center Q. No. 50 A convex lens o ocal length cm is used as a simple microscope by a person having distance o least distinct vision as 0 cm. What is the maximum value o magniying power? Correct Answer For image at least distance, D M=+ 0 =+ cm =+ Q. No. 5 The magniying power o a compound microscope in terms o the magniying power o objective M 0 and that o the eyepiece M e is M0 M M M e 0 e M +M 0 e M M 0 e Correct Answer M = M M eq M=M M 0 e

18 Q. No. 5 Final image produced by the simple microscope is Real and erect Virtual and erect Real inverted Virtual and inverted Correct Answer Q. No. 5 The inal image produced in the compound microscope is Virtual and erect Real and erect Virtual and inverted Real and inverted Correct Answer Q. No. 5 The magniying power o simple microscope can be increased i we use an eyepiece o Large ocal length Smaller ocal length Large diameter Smaller diameter Correct Answer D M= Image at D M=+ Image atleast distance So, M Q. No. 55 The magniying power o simple microscope is + D

19 D + + D D+ Correct Answer D + Q. No. 56 An astronomical telescope essentially consists o Two concave lenses Two convex lenses One concave and one convex lens Two plano concave lenses Correct Answer Two convex lenses Q. No. 57 The resolving power o a telescope can be increased by Increasing the ocal length o objective Increasing the aperture and diameter o objective Decreasing the ocal length o objective Decreasing the aperture diameter o objective Correct Answer d ResolvingPower = whered aperture. Q. No. 5 The ocal length o objective o an astronomical telescope is m. I the magniying power o telescope is 0, then what is length o telescope or relaxed eye? 5 cm 95 cm 05 cm 5 cm Correct Answer Length o telescope = e Incaseo relaxedeye,m= m 00cm 0= e = e 0 = 5cm e So L = 00 cm + 5 cm = 05 cm Q. No. 59 For the normal setting o a telescope Only the object is at ininity Only the inal image is at ininity Both the object and the inal image are at ininity Neither the object nor the inal image has to be at ininity Correct Answer e

20 Both the object and the inal image are at ininity Q. No. 60 In a relecting telescope, the ocal length o the eyepiece is 5 cm. What should be the radius o curvature o the objective mirror to have magniying power o 0? m m m m Correct Answer Telescope ocallength Magniication = Eye.piece ocallength R R 0= 0 = 00 0cm 0 m R= m Q. No. 6 The objective o a telescope has ocal length 0 cm and diameter 5 cm. The ocal length o eyepiece is cm. The magniying power or an object at ininity is Correct Answer 0 0cm M= = =60 e cm M=60 Q. No. 6 The power o the lenses o a telescope are 0.5 and 0 dioptres. Its magniying power is Correct Answer 0 Pe 0 M= = = = 0 e P0 0.5 M= 0 Q. No. 6 The inal image ormed by an astronomical telescope is Virtual and upright Virtual and inverted Real and upright Real and inverted Correct Answer Virtual and inverted

Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi , Ph. : ,

Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi , Ph. : , 1 O P T I C S 1. Define resolving power of a telescope & microscope and give the expression for its resolving power. 2. Explain briefly the formation of mirage in deserts. 3. The radii of curvature of