GEOMETRICAL OPTICS Q. What is meant by relection o light? State and exlain laws o relection with diagrams. (Ans) Relection o light when a light ray moves in a medium and a resistance aears in its way, then the light ray strike with it such that some o its art is absorb by the resistance and most o its art is bounce back in its own medium. This bounce back o light in its own medium is called relection o light. Laws o relection There are two laws o relection o light which are irst o all introduced by a Muslim Scientist Ibnal Haitham. These laws are stated as: (i) First law o relection This law state that the incident ray, relected ray and normal to the oint o incident all lies in the same lane. (ii) Second law o relection This law state that the angle o incidence is always eual to the angle o relection. Mathematically m i mr Q.2 Distinguish between regular and irregular relection o light? Also give its imortance. (Ans) Regular relection o light The relection o light rom a smooth shining surace in which the arallel light rays move arallel ater relection is called Regular relection o light.
Imortance Due to Regular relection o light a driver can see the rear view by the side mirror o the vehicles. Regular relection o light is used in the image ormation by mirrors and microscoe. Irregular relection o light The relection o light rom a rough and uneven shining surace in which all the arallel light rays are scattered in dierent directions ater relection is called Irregular relection o light. Imortance Due to Irregular relection o light we can receive light beore the sun rises and ater the sun set. We can get light in such laces where there is no direct aroach o sun light. Non-luminous objects are also visible due to Irregular relection o light. Q.3 What is sherical mirror? Discuss the tyes o sherical mirrors. (Ans) Sherical mirror The art o the sherical shell having its outer or inner surace is shining and relecting is called sherical mirror. There are two tyes o sherical mirrors. () Concave mirror A sherical mirror whose inner surace is shining and relecting is called concave mirror. A beam o arallel rays o light assing rom a concave mirror ocuses at one oint ater relection. Thereore a concave mirror is also called converging mirror.
(2) Convex mirror A sherical mirror whose outer surace is shining and relecting is called convex mirror. A beam o arallel rays o light assing rom a convex mirror scattered in dierent directions. Thereore a convex mirror is also called diverging mirror. Q.4 Deine the main terms used in sherical mirrors. (Ans) The terms related with sherical mirrors are:. Center o curvature The center o the shere rom which mirror is taken out is called center o curvature. It is denoted by C. As shown below. 2. Radius o curvature The radius o the shere rom which mirror is taken out is called radius o curvature. It is denoted by r. As shown in igure A. 3. Pole The geometrical central oint o the sherical mirror is called ole. It is denoted by P. As shown in igure A. 4. Princial axis The imaginary straight line assing rom the ole P and center o curvature C o the sherical mirror is called rincial axis. As shown in igure A. 5. Aerture The diameter o the circular boundary o the sherical mirror is called aerture. OR The area o the sherical mirror exosed to the incident light is called aerture. As shown in igure A. 6. Princial ocus (OR) Focus oint The oint o a concave mirror at which all the relected rays are seem to converging is called rincial ocus or ocus oint. OR
The oint o a convex mirror rom which all the relected light rays are seem to be diverging is called rincial ocus or ocus oint. It is denoted by F. As shown in igure A. 7. Focal length The distance between the ole and ocus oint o the sherical mirror is called ocal length. It is denoted by. OR Focal length o the concave mirror is taken ositive while the ocal length o the convex mirror is taken negative. As shown in igure A. (Figure A) Relection o Secial rays i. The ray o light arallel to the rincial axis asses through ocus oint o the concave mirror ater relection. ii. The ray o light assing through ocus oint becomes arallel to the rincial axis ater relection rom the mirror. iii. The ray o light assing through the center o curvature o the concave mirror is relected back along the same ath.
iv. The ray o light incident at the ole o a concave mirror is relected back making the same angel o relection with rincial axis as incident ray makes with rincial axis. Q.5 An object is brought rom a long distance towards the sherical mirror. Discuss the eatures o the images with diagram. (Ans) There are ive dierent tyes o images ormed through a concave mirror by bringing object rom a long distance towards the mirror. CASE When an object is laced away rom the center o curvature C o the concave mirror, its image is ormed in between center o curvature C and ocus oint F. The image will be real, inverted and smaller in size that o the object. Diagrammatically
CASE 2 When an object is laced at the center o curvature C o the concave mirror, its image is ormed at the center o curvature C. The image will be real, inverted and o the same size that o the object. Diagrammatically CASE 3 When an object is lace in ront o a concave mirror in between the ocus oint F and center o curvature C, its image is ormed away rom the center o curvature C. the image will be real, inverted and large in size that o the objects. Diagrammatically CASE 4 When an object is laced at the ocus oint F o a concave mirror, its image is ormed at ininity. The image will be real, inverted and larger in size that o the object. Diagrammatically
CASE 5 When an object is laced in between ocus oint F and ole P o the concave mirror, its image is ormed behind the mirror. The image will be virtual, erected and large in size that o the object. Diagrammatically Image ormation through convex mirror When an object is laced in ront o a convex mirror, its image is ormed behind the mirror. The image will be virtual, erected and smaller in size that o the object. Diagrammatically Q.6 Prove mirror ormula or a concave mirror. (Ans) Consider an object AB is laced away rom the center o curvature o a concave mirror, its image A B is ormed in between center o curvature C and ocus oint F. The distance o the object rom the mirror is and distance o the image rom the mirror is. Diagrammatically It is clear rom igure that ABP and ABP are similar. Then
AB BP OR AB BP AB BP () AB BP Similarly PDF and ABF are similar, thereore PD AB PF BF Since PD AB AB PF AB BF AB PF (2) AB BF Comaring euation () and euation (2), we get BP BP PF BF We know rom igure that (A) BP, BP, PF andbp Put these values in euation (A), We get ( ) Now dividing both sides by
It is the reuired mirror ormula or a concave mirror. Q.7 What is linear magniication? Also discuss the sign convention. (Ans) Linear magniication The ratio o the size o the image to the size o the object is called Linear magniication. OR The ratio o the image distance rom the mirror to the object distance is called Linear magniication. It is denoted by M. Mathematically M h h i o Sign convention The distance o the real image rom the mirror is taken ositive, where as the distance o the virtual image rom the mirror is taken negative. The ocal length o a concave mirror is taken ositive and or a convex mirror it is negative. Q.8 Describe the uses o sherical mirrors. (Ans) Uses o sherical mirrors are as under: i. As shaving mirror Concave mirror o large ocal length is used as shaving mirror. When a erson looks his ace through this mirror, an enlarge erect and virtual image is seen in the mirror. ii. By doctors and dentists dentists use a small concave mirror to have a look o backside o tooth and cavity in it. Doctors also use it to examine ear, nose, throat etc. iii. As objective o relecting telescoe A concave mirror o large aerture is used as objective in telescoe. Greater amount o light is incident rom the object, so a clear image can be seen by such telescoe.
iv. In microscoe Concave mirror is used in microscoe to concentrate light on the slide. v. In automobile headlights and search lights Concave mirrors are used behind the bulb such that a bulb lies at their rincial ocus. The rays o light become arallel ater relection. Thus owerul beam o light is obtained in a articular direction by headlights and search lights. vi. In vehicles Convex mirrors are used in vehicles to observe rear view. It makes small, erect and virtual images o the objects behind the vehicle and rovides a wide ield o view. Q.9 Exlain reraction o light? State the laws o reraction. (Ans) Reraction o light When a light ray enters rom one transarent medium into another obliuely, it slightly bends rom its original ath. This behavior o light is called reraction o light. Whenever light ray enters rom a rare medium into a denser medium, the ray o light will slightly bends towards the normal. Air N Water N Whenever light ray enters rom a denser medium into a rare medium, the ray o light will slightly bends away rom the normal. Air N Water N Laws o reraction o light There are two laws o reraction that are as under.
() First law o reraction This law state that the incident ray, reracted ray and normal to the oint o incident all lies in the same lane. (2) Snell s law This law state that the ratio o the sine o angle o incidence to the sine o angle o reraction is constant or a given air o media. Mathematically sini n sin r Q.0 What is meant by reractive index? (Ans) Reractive index It can be deined as the ratio o the seed o light in air or vacuum to the seed o light in the media. It is denoted by n. Mathematically reractiveindex seedolightinairorv acuum seedolightinmedia C n V Where C is the seed o light and its value is 3x0 8 m/sec. Reractive index o some common substances is; Substance Reractive index Substance Reractive index Air 003 Crown 52 glass Ice 3 Kerosene 44 oil Water 33 Diamond 2 42
Q. What is total internal relection o light? Mention some ractical alications o it. (Ans) Total internal relection o light When a ray o light move rom a denser medium to a rare medium, then the light ray bends away rom the normal. As we increase the angle o incidence the corresonding angle o reraction will also increases. At a certain angle o incidence the reracted angle becomes 90, this angle o incidence is called critical angle c. Now i the incident angle is increased rom critical angle the light ray bounce back in its own medium. This behavior o light is called total internal relection o light. There are two conditions or total internal relection o light. (i) The light ray must go rom a denser medium to a rare medium. (ii) The angle o incidence must be greater than critical angle. Relationshi between reractive index and critical angle Consider a light ray enter rom a denser medium to a rare medium, so that the incident angle is critical angle and the reracted angle is 90. n n sin90 sin sin c c Practical alications o total internal relection o light () Periscoe A device used to see objects which are above or below the eye level. It is usually used in submarine and tanks to see objects rom a saer lace. A eriscoe consists o a long tube which is bent at 90 at both ends. At each end a totally relecting rism is ixed.
An object AB is laced in ront o a eriscoe, its image is seen through the eriscoe. Because each o the rism turns the incident ray o light though 90. (2) The binoculars It consists o risms that reduce the length o the device and roduce erect image. The light rays in a air o binoculars are bent through 80 by each rism in contrast to the eriscoe where light rays are only bent through 90 by each rism. Figure (3) Otical ibers An otical iber is made o a core o high reractive index i.e. glass or lastic. It is normally coated with glass o lower reractive index. A light ray introduce into the otical iber will be internally relected at the surace. The thickness o the iber is eual to the thickness o the human hair that is o mm. 00 Uses A bundle o several thousands o such ibers are bound together in a lexible tube called light ie. This light ie is used by the surgeons to examine the interior arts o the body. Otical ibers are also used in telecommunication as it carries inormation aster than other wires like iron, coer, etc.
(4) Endoscoe It is an otical instrument used to view and hotograh a hollow organ inside the body such as the bladder, womb, etc. it works on the rincile o total internal relection o light. A video camera is itted outside the bundle o ibers which can visible the interior organs o the atient which is to be oerated. Q.2 What is meant by an otical rism? How does the angle o deviation can be determined through rism. (Ans) Prism It is a transarent body having three rectangular and two triangular suraces. The three rectangular suraces inclined to each other making a triangular boundary, while the two triangular suraces are arallel to each other. The angle between the two reracting rectangular suraces oosite to the base is called angle o the rism. Angle o the rism is denoted by A.
Determination o angle o deviation Consider the ray o light PQ strikes the ace AB o the rism. The entering ray bends towards the normal as glass is denser than air and roceeded along QR and incident on the ace AC o the rism. The ray RS bends away rom the normal towards the base as air is rare medium and glass is denser. Extend PQ as PT and RS as SE, they meet at oint D. Thus the rism deviate the light ray PT through an angle TDS in the orm o RS. This angle TDS is called angle o deviation. Relation between reractive index and angle o deviation Reractive index o the rism can be calculated as ollow; A Dm sin( ) n 2 A sin 2 Q.3 What is a lens? Exlain the main and sub tyes o lenses. (Ans) Lens A lens is a transarent material usually made o glass which is bounded by a sherical surace at least rom one side. Basically lenses are used to converge or diverge the incident beam o light. There are two main tyes o lenses. () Convex lens (2) Concave lens () Convex lens A tye o lens which is thicker at the center and thinner at the edges is called convex lens. It is also called as converging lens, because it ocus a arallel beam o light at a oint known as ocus oint o the lens. There are three sub tyes o a convex lens. (i) Double convex lens A convex lens whose both bounded suraces are convex is known as double convex lens. (ii) Plano convex lens A convex lens whose one bounded surace is lane and the other is convex is known as Plano convex lens. (iii) Concave convex lens A convex lens whose one bounded surace is concave and the other is convex is known as concave convex lens.
(2) Concave lens A tye o lens which is thinner at the center and thicker at the edges is called convex lens. It is also called as diverging lens, because it scattered the arallel beam o light alls on it. There are three sub tyes o concave lens. (i) (ii) (iii) Double concave lens A concave lens whose both bounded suraces are concave is known as double concave lens. Plano concave lens A concave lens whose one bounded surace is lane and the other is concave is known as Plano concave lens. Convex concave lens A concave lens whose one bounded surace is convex and the other is concave is known as convex concave lens. Q.4 Deine the main terminologies used in lenses? (Ans) The main terminologies used in lenses are; () Otical centre The centre oint o a lens is called otical centre. It is denoted by O. (2) Princial axis The imaginary straight line assing rom the otical centre O and are erendicular to both the aces o the lens is called rincial axis. (3) Princial ocus The oint o a convex lens at which all the reracted rays are seem to converging is called rincial ocus or ocus oint. OR The oint o a concave lens rom which all the reracted light rays are seem to be diverging is called rincial ocus or ocus oint. It is denoted by F. Lenses have two oci and are at eual distance rom the otical centre at either side. (4) Focal length The distance between the otical centre and ocus oint o the sherical mirror is called ocal length. It is denoted by. OR Focal length o the convex lens is taken ositive while the ocal length o the concave lens is taken negative.
(i) (ii) (iii) SPECIAL RAYS DIAGRAM The ray o light through otical centre asses without reraction. The ray o light arallel to the rincial axis asses through ocus oint ater reraction. The ray o light assing through ocus oint moves arallel to the rincial axis ater reraction. Q.6 An object is brought rom a long distance towards the Lens. Discuss the eatures o the images with diagram. (Ans) There are ive dierent tyes o images ormed through a convex lens by bringing object rom a long distance towards the lens. CASE When an object is laced away rom 2F o a convex lens, its image is ormed in between 2F and ocus oint F at other side. The image will be real, inverted and smaller in size that o the object. Diagrammatically CASE 2 When an object is laced at 2F o the convex lens, its image is ormed at 2F at the other side. The image will be real, inverted and o the same size that o the object. Diagrammatically CASE 3 When an object is lace in ront o a convex lens in between the ocus oint F and 2F, its image is ormed away rom the 2F at the other side. The image ormed will be real, inverted and large in size that o the objects.
Diagrammatically CASE 4 When an object is laced at the ocus oint F o a convex lens, its image is ormed at ininity. The image will be real, inverted and larger in size that o the object. Diagrammatically CASE 5 When an object is laced in between ocus oint F and otical centre o the convex lens, its image is ormed in ront o the lens. The image will be virtual, erected and large in size that o the object. Diagrammatically Image ormation through concave lens When an object is laced in ront o a concave lens, its image is ormed in ront o the lens. The image will be virtual, erected and smaller in size that o the object. Diagrammatically Sign convention The distance o the real image rom the lens is taken ositive, where as the distance o the virtual image rom the lens is taken negative. The ocal
length o a convex lens is taken ositive and or a concave lens it is negative. Q.7 Prove lens ormula or a convex lens. (Ans) Consider an object AB is laced in ront o a convex lens, its image A B is ormed behind the lens. The distance o the object rom the lens is and distance o the image rom the lens is. Diagrammatically It is clear rom igure that AB OB OR AB OB ABO and ABO are similar. Then AB OB () AB OB Similarly ODF and ABF are similar, thereore OD AB OF BF Since OD AB AB AB OF BF AB OF (2) AB BF Comaring euation () and euation (2), we get
OB OF (A) OB BF We know rom igure that OB, OB, OF Put these values in euation (A), We get ( ) Now dividing both sides by andob It is the reuired lens ormula or a convex lens. Q.8 What is meant by ower o a lens? (Ans) Power o a lens It can be deined as the recirocal o the ocal length o a lens in meter is called ower o a lens. It is denoted by D. Its SI unit is diotre. The ower o a convex lens is taken ositive, while or a concave mirror it is negative. Mathematically D ( m) Q.9 Write note on the ollowing instruments. (Ans) Simle microscoe A device used to see small objects that cannot be seen though naked eye is called microscoe. Construction It is a convex lens o short ocal length. It is also called magniying glass. It works on the rincile that when an object is laced within its ocal length, a magniied, virtual and erect image is ormed. The image ormed through a microscoe is larger than the object, it becomes easy to study small
objects. Watch maker and jewelers used it to observe small ieces which cannot be seen on naked eyes. Comound microscoe It consist o two convex lenses o short ocal lengths itted at the outer end o two tubes. These tubes can slide into one another to adjust the distance between two lenses. The lens which is towards the object is called objective lens(objective) and the lens which is towards our eyes is called eye iece lens(eye iece). The ocal length o objective lens is shorter than eye iece lens. As a result the image ormed by the microscoe is magniied and erect. Astronomical telescoe A device used to see heavenly objects like sun, stars, moon etc are called telescoe. It consist o two convex lenses called objective and eye iece which are itted at the outer ends o two metallic tubes which can slide into one another. The objective o a telescoe is o larger ocal length and can cature beyond objects, while eye iece is o shorter ocal length can magniied objects.
Q.20 Exlain the main deects o vision. How each deect can be corrected? (Ans) There are two main deects o vision.. Short sightedness(myoia) A erson having this deect can see the near objects clearly but cannot see the object situated at ar distances as much clear and distinctly. The reason o this deect is that the ocal length o the eye lens is very small or the eye ball becomes much larger. Thereore the rays o the ar objects ocus just beore the retina. This deect can be corrected by using a concave lens o suitable ocal length in the sectacles. 2. Long sightedness(hyermetroia) A erson having this deect can see the ar objects clearly but cannot see the near objects clearly. The reason o this deect is that the ocal length o the eye lens is very large or the eye ball becomes small. Thereore the rays o the near objects ocus behind the retina. This deect can be corrected by using a convex lens o suitable ocal length in the sectacles.
SHORT QUESTIONS i. Draw a label diagram to show the: (a) Pole (b) Centre o curvature (c) Princial axis (d) Princial ocus (e) Radius o curvature Ans. See Q.4 ii. Deine ocal length and radius o curvature. What is the relation between ocal length and radius o curvature in case o a concave mirror? Ans. Radius o curvature The radius o the shere rom which mirror is taken out is called radius o curvature. It is denoted by r. Focal length The distance between the ole and ocus oint o the sherical mirror is called ocal length. It is denoted by. OR Focal length o the concave mirror is taken ositive while the ocal length o the convex mirror is taken negative. Relation between ocal length and radius o curvature Focal length is hal o the radius o curvature. Mathematically r 2 iii. Name the sherical mirror which has: (a) Virtual rincial ocus (b) Real rincial ocus Ans. (a) Convex mirror has virtual rincial ocus. (b) Concave mirror has real rincial ocus. iv. I the radius o curvature o a concave mirror is m, what is its ocal length? Ans. I radius o curvature o the concave mirror is m, then its ocal length is 0.5m. Mathematically r 0 5m 2 2 v. For what osition o an object, a concave mirror orms an image which is real and eual in size to the object? Ans. When an object is laced at the center o curvature C o the concave mirror, its image is ormed at the center o curvature C. The image will be real, inverted and o the same size that o the object. Diagrammatically
vi. For what osition o an object a real and diminished image is ormed by a concave mirror? Ans. When an object is laced away rom the center o curvature C o the concave mirror, its image is ormed in between center o curvature C and ocus oint F. The image will be real and diminished. Diagrammatically vii. Give at least three uses o a concave mirror? Ans. See Q.8 viii. Deine reractive index. How is it related to velocity o light on a air o media? Ans. See Q.0 ix. How would you make the rays rom a luminous bulb arallel by means o a concave mirror? Ans. It is clear rom ray diagram that i we lace the luminous bulb at the ocus oint o the concave mirror, the light rays will move arallel. These light rays meet at ininity. x. What is meant by linear magniication o an image by a sherical mirror? Ans. See Q.7 xi. Which tye o sherical mirror has a wider ield o view? Ans. The convex mirror has a wider ield o view, because it roduce virtual, erect and diminished image o an object laced in ront o it. It is used in automobile to see the image o the object coming behind the automobiles. xii. Why does a driver reer to use a convex mirror as a back view mirror in an automobile? Ans. A driver reer to use a convex mirror as a back view mirror in automobile, because it roduce virtual, erect and diminished image o an object laced in ront o it. As a result the driver can judge about every thing coming behind his vehicle. Thus a convex mirror rovides us the way o sae driving. xiii. A ray o light traveling in water emerges into air. Draw a ray diagram indicating the change in its ath? Ans. Whenever light ray enters rom a denser medium into a rare medium, the ray o light will slightly bends away rom the normal. As water is denser
medium and air is rare medium, so the ray o light slightly bends away rom the normal. Diagrammatically Air N Water N / xiv. What is the unit o reractive index? Ans. Reractive index is the ratio o two similar uantities. Thereore it has no unit. Mathematically reractiveindex n C V seedolightinairorv acuum seedolightinmedia xv. Which one has higher reractive index, water or glass? Ans. The reractive index o glass is greater than that o water. The reractive index o water is.33, while the reractive index o various glasses ranges rom.5 to.9. xvi. Deine Snell s law o reraction? Ans. Snell s law This law states that the ratio o the sine o angle o incidence to the sine o angle o reraction is constant or a given air o media. Mathematically sini n sin r xvii. Why a encil hal immersed in water and held obliuely, aears to be bent at the water surace? Ans. It is because o reraction o light, the light rays coming rom water (denser medium) into air (rare medium). The light rays bends away rom the normal. As a result the encil aears to be bent at the water surace. xviii. For what osition an object, a real and diminished image ormed by convex lens?
Ans. When an object is laced away rom 2F o a convex lens, its image is ormed in between 2F and ocus oint F at other side. The image will be real, inverted and smaller in size that o the object. Diagrammatically xix. What is the SI unit o ower o a lens? Ans. The unit o the ower o a lens is diotre. It can be deined as the ower o a lens is one diotre i the ocal length o the lens is one meter. xx. What will be the value o angle o reraction when angle o incidence in denser medium is eual to the critical angle or a given air o media? Ans. When a ray o light move rom a denser medium to a rare medium, then the light ray bends away rom the normal. As we increase the angle o incidence the corresonding angle o reraction will also increases. At a certain angle o incidence the reracted angle becomes 90, this angle o incidence is called critical angle c. The angle o reraction or the given air o media will be 90 0. xxi. Why do stars twinkle on a clear night? Ans. The light rom the stars travels through dierent layers o the atmoshere o various densities. Thereore the light rays deviate rom its original ath time to time. As a result it looks like that stars are twinkling. xxii. You are given two convex lenses o ocal length 7cm and 20cm. which one will you choose as objective lens or making a comound microscoe? Ans. The magniying ower o a comound microscoe can be stated as; L d M ( ) 0 e Smaller the ocal length o objective lens greater will be the magniying ower. So we will choose the lens having ocal length 7cm. xxiii. What tye o lens is used to make the eye-iece o a comound microscoe? Ans. The eye-iece o a comound microscoe is a convex lens o larger aerture and ocal length as comared to objective lens.
xxiv. In a telescoe, which one has a shorter ocal length, objective or eyeiece? Ans. The magniying ower o a telescoe can be stated as; o M e We use an eye-iece o short ocal length and small aerture. xxv. A child sitting in a classroom is not able to see clearly the writing on the blackboard? (a) Name the tye o deect rom which he suering? (b) With the hel o ray diagram, show that how this deect can be removed? Ans. A child sitting in a classroom is not able to see clearly the writing on the blackboard. (a) The deect rom which the child suering is called short sightedness or myoia. (b) This deect can be corrected by using a concave lens o suitable ocal length in the sectacles.
NUMERICAL PROBLEMS. The image o an object is ormed by a concave mirror at a distance o 30cm. ind the osition o an object i the ocal length o concave mirror is 5cm. Given data 30cm 5cm? We know that 5 2 30 30 30cm 30 2. Find the osition o an object to be laced in ront o a concave mirror o radius o curvature 8cm to get a real image in double in size. Given data? M 2 r 8cm r 8 2 2 We know that M 2 9cm 2 We also know that
9 9 2 2 27 2 2 35cm 3. A candle lame is situated at a distance o 40cm rom a convex mirror i radius o curvature o mirror is 40cm. ind the osition and nature o the image. Given data 40cm r 40cm r 2? Nature? We know that 3 40 40 3 40 2 20 2 40 20cm 40 333cm Nature: Image is virtual ( = 3.33cm)
4. Determine the reractive index o water i the seed o light in water is 2.25x0 8 m/s and velocity o light in air is 3x0 8 m/s? Given data V 2 250 C 30 n? 8 8 m / s C n V 8 30 n 2 250 n 33 8 m / s 5. A ray o light is incident on the surace o Sulhuric acid at 35 0 angle o incident. The reractive index o Sulhuric acid is.43. Find the angle o reraction o the reracted ray. Given data mi mr 35? n 43 sini n sinr Sin35 Sinr.43 0 573 Sinr 43 mr Sin (0 40) mr 236 6. An object 5cm high laced in ront o a convex lens o ocal length 20cm. ind the osition o the object i a real image 0cm high is to be obtained. Given data h 5cm h o i 0cm 20cm? We know that
h h M o i 2 2 5 0 We also know that cm 30 2 60 60 2 2 2 20 2 20 7. Find the ocal length o a convex lens whose ower is 5 diotre. Given data cm m D D diotre D 20 2 0 5? 5 8. A converging lens o ocal length 5cm is laced 20cm in ront o a screen. Where should the object be laced i its image is aear on the screen?
Given data? 20 5 cm cm We know that cm 60 60 60 3 4 20 5