19 - RAY OPTICS Page 1 ( Answers at the end of all questions )

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1 19 - RAY OPTICS Page 1 1 ) A ish looking up through the water sees the outside world contained in a circular horizon. I the reractive index o water is 4 / 3 and the ish is 1 cm below the surace, the radius o this circle in cm is ( a ) 36 / 7 ( b ) 36 7 ( c ) 4 5 ( d ) 36 / 5 [ AIEEE 005 ] ) A thin glass ( reractive index 1.5 ) lens has optical power - 5 D in air. It opti al power in a liquid medium with reractive index 1.6 will be ( a ) - 1 D ( b ) 1 D ( c ) - 5 D ( d ) 5 D [ AIEEE 005 ] 3 ) A light ray is incident perpendicular to one ace o a 90 prism and is totally internally relected at the glass-air interace. I the angle o relection is 45, we conclude that the reractive index, n: ( a ) n < 1 / ( b ) n > ( c ) n > 1 / ( d ) n < [ AIEEE 004 ] 4 ) A plano-convex lens o reractive index 1.5 and radius o curvature 30 cm is silvered at the curved surace. Now this lens has b en used to orm the image o an object. At what distance rom this lens, an obj ct be placed in order to have a real image o the size o the object? ( a ) 0 cm ( b ) 30 cm ( c ) 60 cm ( d ) 80 cm [ AIEEE 004 ] 5 ) To get three images o a single bject, one should have two plane mirrors at an angle o ( a ) 30 ( b ) 60 ( c ) 90 ( d ) 10 [ AIEEE 003 ] 6 ) The image ormed by n objective o a compound microscope is ( a ) real and enlarged ( b ) virtual and enlarged ( c ) real and diminished ( d ) virtual and diminished [ AIEEE 003 ] 7 ) A candle placed 3 cm rom a lens, orms an image on a screen placed 75 cm on the other end o the lens. The ocal length and type o the lens should be ( a ) m and convex lens ( b ) cm and concave lens ( c ) 0.5 cm and convex lens ( d ) cm and concave lens [ AIEEE 003 ] 8 ) A person having the nearest distance o distinct vision o 3 cm uses a reading lens o 8 cm ocal length. The magniication o his reading lens is ( a ) 5 ( b ) 4 ( c ) 3 ( d ) [ AIEEE 00] 9 ) Consider telecommunication through optical ibres. Which o the ollowing statements is not true? ( a ) Optical ibres can be o graded reractive index. ( b ) Optical ibres have extremely low transmission loss. ( c ) Optical ibres are subject to electromagnetic intererence rom outside. ( d ) Optical ibres may have homogeneous core with a suitable cladding. [ AIEEE 00 ] 10 ) A ray o light passing through a prism having µ = suers minimum deviation. I angle o incidence is double the angle o reraction within prism, the angle o prism is ( a ) 30 ( b ) 45 ( c ) 60 ( d ) 90 [ AIEEE 00 ]

2 19 - RAY OPTICS Page 11 ) The combined power o two lenses in contact is + 10 D. When they are separated by 0 cm, their power becomes D. The powers o these lenses are ( a ) D, D ( b ) D, +.5 D ( c ) D, +.5 D ( d ) D, D [ AIEEE 00 ] 1 ) A ray o light is incident on the ace AB o a prism o reracting angle 60 as shown in the igure. The angle o incidence at which the ray o light just suers total internal relection on the ace AC is ( µ = 1.5 ) ( a ) 19.6 ( b ) 3.6 ( c ) 7.6 ( d ) 35.6 [ AIEEE 00 ] 13 ) A double convex lens o reractive index µ is immers d in a liquid o reractive index µ 1. This lens will act as converging lens, i ( a ) µ 1 > µ ( b ) µ > µ 1 ( c ) µ 1 = µ ( d ) µ 1 = µ = 0 [ AIEEE 00 ] 14 ) A convex lens is in contact with concave ens The magnitude o the ratio o their ocal lengths is / 3. Their equivalent oca ength is 30 cm. Their individual ocal lengths are ( a ) - 75, 50 ( b ) - 10, 15 ( c ) 75, 50 ( d ) - 15, 10 [ IIT 005 ] 15 ) A container is illed with water ( m = 1.3 ) upto a height o 33.5 cm. A concave mirror is placed 15 cm above the water level and the image o an object placed at the bottom is ormed 5 cm below he water level. The ocal length o the mirror is ( a ) 10 cm ( b ) 15 cm ( c ) 0 cm ( d ) 5 cm [ IIT 005 ] 16 ) White light is incident n the interace o glass and air as shown in the igure. I green light is just totally internally relected, then the emerging ray in air contains ( a ) yellow, orange, red ( b ) violet indigo, blue ( c ) al ol urs ( d ) all colours except green [ IIT 004 ] 17 ) A ray o light is incident on an equilateral glass prism placed on a horizontal table. Which o the ollowing is true or maximum deviation? ( a ) PQ is horizontal ( b ) QR is horizontal ( c ) RS is horizontal ( d ) either PQ or RS is horizontal [ IIT 004 ] 18 ) A point object is placed at the centre o a glass sphere o radius 6 cm and reractive index 1.5. The distance o the virtual image rom the surace o the sphere is ( a ) cm ( b ) 4 cm ( c ) 6 cm ( d ) 1 cm [ IIT 004 ]

3 19 - RAY OPTICS Page 3 19 ) The size o the image o an object, which is at ininity, as ormed by a convex lens o ocal length 30 cm is cm. I a concave length o ocal length 0 cm is placed between the convex lens and the image at a distance o 6 cm rom the convex lens, the size o the new image will be ( a ) 1.5 cm ( b ).5 cm ( c ) 1.05 cm ( d ) cm [ IIT 003 ] 0 ) A ray o light is incident at the glass-water interace at an angle i. I it emerges inally parallel to the surace o water, then the value o µ g would be ( a ) ( 4 / 3 ) sin i ( b ) 1 / sin i ( c ) 4 / 3 ( d ) 1 [ IIT 003 ] 1 ) An observer can see through a pin-hole the top end o a thin rod o height h, placed as shown in the igure. The bea er height is 3h and its radius is h. When the beaker is illed with a liquid upto a height h, he can see the lower end o the rod. Then the reractive index o the liquid is ( a ) 5 ( b ) 5 ( c ) 3 ( d ) 3 [ IIT 00 ] ) Which one o the ollowing spherical lenses does not exhibit dispersion? The radii o curvature o the suraces o the lenses ar given in the diagrams. [ IIT 00 ] 3 ) Two plan mirrors A and B are aligned parallel to each other as sown in the igure. A light ray is incident at an angle o 30 at a point just inside one end o A. The plane o incidence coincides with the plane o the igure. The maximum number o times the ray undergoes relections ( including the irst one ) beore it emerges out is ( a ) 8 ( b ) 30 ( c ) 3 ( d ) 34 [ IIT 00 ] ) A ray o light passes through our transparent media with reractive indices µ 1, µ, µ 3 and µ 4 as shown in the igure. The suraces o all media are parallel. I the emergent ray CD is parallel to the incident ray AB, we must have ( a ) µ 1 = µ ( b ) µ = µ 3 ( c ) µ 3 = µ 4 ( d ) µ 4 = µ 1 [ IIT 001 ]

4 19 - RAY OPTICS Page 4 5 ) A given ray o light suers minimum deviation in an equilateral prism P. Additional prisms Q and R o identical shape and o the same material as P are now added as shown in the igure. The ray will suer ( a ) greater deviation ( b ) same deviation as beore ( c ) no deviation ( d ) total internal relection [ IIT 001 ] 6 ) A point source o light B, placed at a distance L in ront o the centre o a mirror o width d, hangs vertically on a wall. A man walks in ront o the mirror along a line parallel to the mirror at a distance L rom it as shown. The greatest distance over which he can see the image o the light source in the mirror is ( a ) d / ( b ) d ( c ) d ( d ) 3d [ II 000] 7 ) In a compound microscope, the intermediate image is ( a ) virtual, erect and magniied ( b ) eal erect and magniied ( c ) real, inverted and magniied ( d ) vir ual erect and reduced [ IIT 000 ] 8 ) A diverging beam o light rom a point source S having divergence angle α is in ident symmetrically on a glass slab as shown. Th angles o incidence o the two extreme rays are equal I the thickness o the glass slab is t and ts e active index is n, then the divergent angle o the eme gent beam is ( a ) zero ( b ) α ( c ) sin -1 (1/n) ( d ) sin - 1 ( 1 / n ) [ IIT 000 ] 9 ) A rectangular glass slab ABCD o reractive index n 1 is immersed in water o reractive index n ( n 1 > n ) A ray o light is incident at the su ace AB o the slab as shown. The maximum value o the angle o incidence α max, such that he ay comes out only rom the other surace CD, is given by ( a ) - 1 n 1-1 n sin cos sin ( b ) - 1 n n sin n1 cos sin 1 n ( c ) 1 n 1 sin - ( d ) n 1 n sin - [ IIT 000 ] n1 30 ) A hollow double concave lens is made o very thin transparent material. It can be illed with air or either o two liquids L 1 or L having reractive indices n 1 and n respectively ( n > n 1 > 1 ). The lens will diverge a parallel beam o light i its is illed with ( a ) air and placed in air ( b ) air and immersed in L 1 ( c ) L 1 and immersed in L ( d ) L and immersed in L 1 [ IIT 000 ]

5 19 - RAY OPTICS Page 5 31 ) A concave lens o glass, reractive index 1.5 has both suraces o same radius o curvature R. On immersion in a medium o reractive index 1.75, it will behave as a ( a ) convergent lens o ocal length 3.5 R ( b ) convergent lens o ocal length 3.0 R ( c ) divergent lens o ocal length 3.5 R ( d ) divergent lens o ocal length 3.0 R [ IIT 1999 ] 3 ) A real image o a distant object is ormed by a planoconvex lens on its principal axis. Spherical aberration ( a ) is absent ( b ) is smaller i the curved surace o the lens aces the object ( c ) is smaller i the plane surace o the lens aces the obj ct ( d ) is the same whichever side o the lens aces the object [ IIT 1998 ] 33 ) A ray o light traveling in a transparent medium is incident on a surace separating the medium rom air at an angle o incidence 45. The ay undergoes total internal relection. I n is the reractive index the medium with respect to air, select the possible value ( s ) o n rom the ollowing. ( a ) 1.3 ( b ) 1.4 ( c ) 1.5 ( d ) 1 6 [ IIT 1998 ] 34 ) A concave mirror is placed on a h rizontal table with its axis directed vertically upwards. Let O be the pole o the mi or and C its centre o curvature. A point object is placed at C. It has a real imag, als located at C. I the mirror is now illed with water, the image will be ( a ) real and will remain at C ( b ) real and located at a point between C and ( c ) virtual and located at a point between C and O ( d ) real and located at a point between C and O [ IIT 1998 ] 35 ) A spherical surace o radius o curvature R, separates air ( reractive index 1.0 ) rom glass ( reractive index 1.5 ). The centre o curvature is in the glass. A point object P placed in air is ound to have a real image Q in the glass. The line PQ cuts the surace at a p int O and PO = OQ. The distance PO is equal to ( a ) 5R ( b ) 3R ( c ) R ( d ) 1.5R [ IIT 1998 ] 36 ) Which o he ollowing orm ( s ) a virtual and erect image or all positions o the object? ( a ) convex lens ( b ) concave lens ( c convex mirror ( d ) concave mirror [ IIT 1996 ] 37 ) Spherical aberration in a thin lens can be reduced by ( a ) using a monochromatic light ( b ) using a doublet combination ( c ) using a circular annular mask over the lens ( d ) increasing the size o the lens [ IIT 1994 ] 38 ) A planet is observed by an astronomical reracting telescope having an objective o ocal length 16 m and an eyepiece o ocal length cm. Which o the ollowing statements are true? ( a ) The distance between the objective and the eyepiece is 16.0 m. ( b ) The angular magniication o the planet is ( c ) The image o the planet is inverted. ( d ) The objective is larger than the eyepiece. [ IIT 199 ]

6 19 - RAY OPTICS Page 6 39 ) A thin prism P 1 with angle 4 and made o glass having reractive index 1.54 is combined with another thin prism P made o glass having reractive index 1.7 to produce dispersion without deviation. The angle o the prism P is ( a ) 5.33 ( b ) 4 ( c ) 3 ( d ).6 [ IIT 1990 ] 40 ) Two thin convex lenses o ocal lengths 1 and are separated by a horizontal distance d ( where d < 1 and d < ), and their centres are displaced by a vertical separation as shown in the igure. Taking the origin o coordinates, O, at the centre o the irst lens, the x and y coordinates o the ocal point o the lens system, or a parallel beam o rays coming rom the let, are given by ( a ) x =, y = ( b ) x = 1 ( + d ), y = d 1 + ( c ) x = + d ( - d ) (, y = 1 d ) + - d - d ( d ) x = + d ( - d ) + - d, y 0 [ IIT 1993 ] 41 ) A beam o light consisting o ed green and blue colours is incident on a right-angled prism as shown in the igure. The reractive indices o the material o the prism or the red, green and blue wavelengths are 1.39, 1.44 and 1.47 respective y. The prism will ( a ) separate pa t o the red colour rom the green and blue colour ( b ) separate part o the blue colour rom the red and g een colours ( c ) separate all the three colours rom one another ( d ) not separate even partially any colour rom the other two colours [ IIT 1989 ] 4 ) An astronomical telescope has an angular magniication o magnitude 5 or distant objects. The separation between the objective and the eye-piece is 36 cm and the inal image is ormed at ininity. The ocal length 0 o the objective and e o the eyepiece are ( a ) 45 cm and - 9 cm ( b ) 50 cm and 10 cm ( c ) 7. cm and 5 cm ( d ) 30 cm and 6 cm [ IIT 1989 ] 43 ) A short linear object o length b lies along the axis o a concave mirror o ocal length at a distance u rom the pole o the mirror. The size o the image is approximately equal to ( a ) b u - 1 ( b ) b u - 1 u - ( c ) b ( d ) b u - [ IIT 1988 ]

7 19 - RAY OPTICS Page 7 44 ) A converging lens is used to orm an image on a screen. When the upper hal o the lens is covered by an opaque screen ( a ) hal the image will disappear ( b ) complete image will be ormed ( c ) intensity o the image will increase ( d ) intensity o the image will dec ase [ IIT 1986 ] 45 ) A ray o light rom a denser medium strikes a rarer medium at an angle o incidence i ( see igure ). The relected and reracted rays make an angle o 90 with each other. The angles o relection and reraction are r and r. The critical angle is ( a ) sin - 1 ( tan r ) ( b ) sin - 1 ( tan r ) ( c ) sin - 1 ( tan i ) ( d ) tan - 1 ( sin i ) [ IIT 1983 ] 46 ) A convex lens o ocal length 40 cm is in con act with a concave lens o ocal length 5 cm. The power o the combination in diopters is ( a ) ( b ) ( c ) + 6 ( d ) [ IIT 198 ] 47 ) A glass prism o reractive index 1.5 is immersed in water ( reractive index 4 / 3 ). A light b am incident normally on the ace AB ( see igure ) is to ally relected to reach the ace BC, i ( a ) sin θ 9 8 ( b ) 3 sin θ < 9 8 ( c ) sin θ 3 [ IIT 1981 ] 48 ) When a ray o light enters a glass slab rom air ( a ) its wavel ngth increases ( b ) neither its wavelength nor its requency changes ( c ) i s requency increases ( d ) its wavelength decreases [ IIT 1980 ] 49 ) An el tric bulb illuminates a plane surace. The intensity o illumination on the surace at point m away rom the bulb is 5 x 10-4 phot ( lumens per sq. cm. ). The line joining the bulb to the point makes an angle o 60 with the normal to the surace. The intensity o the bulb in candela (candle power ) is ( a ) 40 3 ( b ) 40 ( c ) 0 ( d ) 40 x 10-4 [ IIT 1980 ] 50 ) Two plane mirrors are inclined to each other at an angle θ. I a ray o light incident on the irst mirror is parallel to the second mirror and that relected rom the second mirror is parallel to the second mirror, then the angle θ is ( a ) 30 ( b ) 45 ( c ) 60 ( d ) 75

8 19 - RAY OPTICS Page 8 51 ) A lens made o a material o reractive index µ is immersed in a medium o reractive index µ 1. I the radii o curvature o the lens suraces are R 1 and R, then the ocal length o the lens is given by 1 ( a ) µ = ( µ - 1) - ( b ) 1 1 = R 1 R µ 1 R 1 R 1 µ ( c ) = µ ( d ) = µ 1 R 1 R µ R 1 R Answers a b b a c a a a c d c c b d a c b c b b b c b d b d c b a d a b c d d a b,c c a,c,d c c,d c d d b,d a,c a a d b b