Geometrical Optics Questions and Answers

The refractive indices of flint glass for red yellow and violet light are 1 613 1 620 and 1 632 respectively What is dispersive power of flint glass 0 031 0 23 0 016

58 A diverging lens of focal length 10 cm is placed 10 cm in front of a plane mirror as shown in the figure Light from a very far away source falls on the lens The final image is at a distance 10 cm 10 cm R fra fafata 1 20 cm behind the mirror 3 7 5 cm behind the mirror 1 20 cm 3 7 5 cm 2 7 5 cm in front of the mirror 4 2 5 cm in front of the mirror 7 5 cm 2 4 2 5 cm

O 15 cm A concave mirror is moving with velocity 41 21 cm s whereas a point object is moving with 8i 11j cms as shown in figure The object is at a distance of 15 cm in front of mirror whose focal length is 10 cm The axial velocity of image is v then 4xn find the value of n

The refractive index of material of plano convex lens if the radius of curvature of convex lens is 20 cm and focal length is 60 cm will be wich 43 1 2

liquid of refractive index u is poured on glass g 1 5 slab to form a thin layer c g thickness t 2 5 A monochromatic ligh beam of wavelength is incident at small angl with normal For normal viewing of reflecte light Which of the following is are not correct 1 If 1 6 minimum will be observed 2 If 1 8 maximum will be observed 3 If u 1 4 minimum will be observed 4 If u 1 3 maximum will be observed

A small insect is at 60 cm from a concave mirror of focal length 20 cm What is the image distance from the mirror 30 cm 20 cm 15 cm 18 cm

Case Study 2 An art projector is equipment used by artists to create exact copies of artwork to enlarge artwork or to reduce artwork A basic art projector used a light bulb and a lens within a box The light rays from art work being copied are collected onto a lense at single point The lens then projects the image of art work onto the a screen as shown Projector Art work Lens Bulb light SOUTCO Image G

QNO 135 View In English An astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively To view an object 200 cm away from the objective the lenses must be separated b distance 0 4 Correct Answer 4 Status unattempted 373 cm 46 0 cm 50 0 cm 54 0 cm

The refractive index of the glass prism shown in the figure is 2 for green light a ray of cyan colour light is incidence a tp on the face bc of the prism from which side would the light emerge Given the critical angle for blue colour is gr eater than 15 50 The refractive index of the glass prism shown in the figure is 2 for green light A ray of cyan colour light is incident at P on the face BC of the prism From which side would the light emerge Given the critical angle for blue colour is greater than 15 CYAN B C 60 45

Focal length of a thin convex lens is 30 cm At a distance of 10 cm from the lens there is a plane refracting surface of refractive index Where will the parallel rays incident On lens converge a At a distance of 25 cm from the lens b At a distance of 27 5 cm from the lens c At a distance of 40 cm from the lens d At a distance of 45 cm from the lens 3 S 2 A

A virtual erect and magnified image of a real object can be formed by A Plane mirror B Concave mirror C Convex mirror D Concave lens E Convex lens The correct option is A C and D B and E C and E A B and E

Retraction of light through a triangular glass prism is shown in figure The angle of incidence angle of emergence and angle of deviation are represented by respectively for y x Z y z p y p z x p y

In the figure shown sound waves A and B both of A wavelength are initially in phase and travelling rightward as indicated by the two rays Wave A is reflected from four parallel surfaces but ends up travelling in original direction The possible value s of distance L in terms of wavelength in figure which put A and B exactly out of phase with each other after all the reflections is are A 2 2 C 32 4 B 32 2 D 2 mih B

Q4 You are being given the following two spherical surfaces 3 a Denser Convex Spherical surface for the propagation of the light rays from rarer Air to denser medium b Denser Concave Spherical surface for the propagation of the light rays from denser medium to Rarer Air If you join above two equations for the combination of a and b what would you get

3 f 12 cm 4 f 12 cm A beam of light is converging towards a point I on 9 a screen A plane glass plate whose thickness in the direction of the beam 1 refractive index is introduced in the path of the beam The convergence point is shifted by 1 1 away 2 1 1 1 3 t 1 2 4 1 away nearer nearer 3 f 12 cm 4 f 12 cm fur fare face 1 x furuka for r H fax garran at efter for freunfo 1 1 1 1 2 Telegram nequestionpaper 3 1 1 1 4 1 1 1 18 are en

A layer of oil 3 cm thick is floating on a layer of coloured 5 water 5 cm thick Refractive index of coloured water is 3 36 and apparent depth of two liquids appears to be 7 What is refractive index of oil O 1 2 O 1 3 O 1 4 1 52 cm

A converging lens of focal length 50 cm is placed co axially in contact with another lens of unknown focal length If the combination behaves like a diverging lens of focal length 50 cm What is power of second lens 2 D 2 D 4 D 4 D

4 The air bubble cannot form a real image A bi convex lens is formed with two 5 thin plano convex lenses as shown in the figure Refractive index n of the first lens is 1 5 and that of the second lens is 1 2 Both the curved surface area of the same radius of curvature R 14 cm For this bi convex lens for an object distance of 40cm the image distance will be n 1 5 1 280 0 cm 3 21 5 cm R 14cm n 1 2 2 40 0 cm 4 13 5 cm 4 gegen af fafara anar en fax fax for 1 1 2 R 14 cm falfa 40 cm fe fafara X n 1 5 Telegram question paper 1 280 0 cm 3 21 5 cm R 14cm an n 1 2 2 40 0 cm 4 13 5 cm

A prism having an apex angle 4 and refraction 3 index 1 5 is located in front of a vertical plane mirror as shown in figure Through what total angle is the ray deviated after reflection from the mirror 1 176 3 178 90 2 4 4 2 er a cada farger f ffer 1 176 3 178 41 5 1 arx fena una 90 2 4 4 2

2 A plano convex thin lens of focal length 10cm is 12 silvered at its plane surface The distance d at which an object must be kept in order to get its image on itself is 2 20cm 4 2 5cm 10 T A Z unde ve u u af fr f fated and deg Telegram ne questionpaper 1 Sem 3 10cm 3 A body of mass m is situated at distance 4R 13 1 5cm 3 10cm 2 20cm 4 2 5cm mayat 4R

3 4 n 1 The speed of light in media M and M is 1 5 10 m s 2 and 2 0 x 10 m s respectively A ray of light enters from medium M to M at an incidence angle i If the ray suffers total internal reflection the value of iis 1 Equal to or less than sin 2 greater than sin 3 Less than sin 4 Equal to sin cilm cilm 35 3 1 5 10 m s 320 10 ms M M 2 SINH N TH NH NHAU I g i Se HAB 2 sin 2 sefires H 1 sin sin stionplay 4 sin 2 3 4 n 1 f CLICK H apert

If magnitude of dispersive power of two lens are 6 0 024 and 0 036 then focal length be for aberration free combination 2 30 cm 45 cm 4 20 cm 35 cm 1 30 cm 40 cm 3 10 cm 30 cm atau fac d 0 02 3IT 0 036 370 KHI PH I K T KHI I 1 30 cm 40 cm 3 10 cm 30 cm 2 30 cm 45 cm 4 20 cm 35 cm

A converging beam of light is incident on a concave lens of focal length 20 cm In the absence of lens the beam converges at a point 10 cm behind the lens At what point the beam will converge diverge after refraction Converges to 5 cm behind the lens Diverges to 10 cm behind the lens Converges to 6 cm behind the lens Converges to 20 cm behind the lens

A shortsighted person can read a book clearly at 8 a distance 10 cm from the eyes Find the lens required to read the book kept at 60 cm 1 f 30 cm 2 f 30 cm 3 f 12 cm 4 f 12 cm A beam of light is converging towards a point I on 9 fffff 10 cm fer for 1 f 30 cm 3 f 12 cm a 60 cm any 2 f 30 cm 4 f 12 cm far far fund a

The figure shows a transparent sphere of radius R and refractive index u An object O is placed at a distance x from the pole of the first surface so that a real image is formed at the pole of the exactly opposite surface Air X A If x 2R then the value of u is 3 C If x 2R then the value of u is 2 2R B If x then the value of u is 2 D If x then the value of u is 3

3 A convex lens L and a concave lens L have refractive index Match the following two columns 2 Column l A L is immersed in a liquid of refractive 7 index B L is immersed in a liquid of refractive 8 index C L is immersed in a liquid of refractive 7 index D L is immersed in a liquid of refractive 8 index Column II p Lens will behave as convex lens q Lens will behave as concave lens r Magnitude of power of lens will increase s Magnitude of power of lens will decrease dations

If refractive index of material except vacuum for different colour will be different and variation is given as du d a where is wavelength and wavelength increases as we go along V I B G Y OR Choose the incorrect statement s A deviation will be maximum for red through any prism B white light goes from air to matter will disperse in different colours C white light goes from air to matter then violet will be closest to normal in emergent light D deviation will be maximum for violet A

A convex surface of radius of curvature 40 cm separates tw 4 medium of refractive indices and 1 50 An object is kept 3 in the first medium at distance of 20 cm from the convex surface What is image position 24 cm from pole 30 cm from pole 18 cm from pole 36 cm from pole

A disc is placed on the surface of pond with liquid of 5 refractive index A source of light is placed 4 m below the 3 surface What is minimum area of the disc so that light does not come out of liquid 28 26 m 42 4 m 32 62 m 32 6 m

3 2 Find the distance between the images formed by the concave mirror due to this light In Fig 1 372 L is a converging lens of focal length 10 cm and M is a concave mirror of radius of curvature 20 cm A point object O is placed in front of the lens at a distance of 15 cm AB and CD are optical axes of the lens and mirror respectively Find the distance of the final image formed by this system from the optical center of the lens The distance between CD and AB is 1 cm L A O 15 cm C 45 cm D 1 cm B

Answer Q No 4 and 5 by appropriate matching the lists based on the information given in the paragra pole of a silvered equiconvex lens as shown List I contains speed of image v with respect to object focal leng A small lateral object initially at a distance of 30 cm start moving at t 0 with initial velocity 5 m s toward n of above mirror magnitude only and magnification m of object List 1 V in cm s II Nature of image 1 III f in cm t IV Magnification magnitude only 5 m s 30 cm 3 2 R 10 cm List II P 2 5 Q Less than one 410 81 R 610 S 121 T Real U Virtual For the shown above arrangement choose the correct option for time t 0

Latin A phonon with wave vector gets absorbed on collision with an electron of wave vector k The electron is considered free and its energy is much larger than that of the phonon If the electron is scattered at an angle a show that 2 in g 2k 2 31

Two concave refracting surfaces of equal radii of curvature face each other in air as shown in figure A point object O is placed midway between the centre and one of the poles Then the separation between the images of O formed by each refracting surfaces is 1 1 5 glass 1 11 4 R 3 0 114 R n 1 5 glass 2 1 14 R 4 0 0114 R

A Plane mirror is placed on the other side of a convex lens having a focal length of 12 cm A distinct image is formed in front of the lens towards the object when the plane mirror is at a distance of 45 cm from the lens calculate the distance of image from the lens

1 A Galileo telescope has an objective of foca length 100 cm magnifying power 50 The distance between the two lenses in norma adjustment will be A 150 cm C 98 cm B 100 cm D 200 cm

index of medium I and medium II can be changed and hypothetically their ranges are given by 1 and 1 0 Medium II H2 Medium I 40 H1 8 80 8 An experiment is performed keeping i 60 as constant First 2 is increased from 1 to infinity keeping 1 and deviation is calculated Then the refractive index of medium I is increased from 1 to infinity keeping 2 1 and deviation is noted Now an approximate graph between and k 1 2 is plotted which is shown in the figure Read the above passage carefully and answer the following question Region i 60 1 1 0 2 0 1 5 I I I N 1 ko Interface Region The value of ko is equal to Region III k

Assuming human pupil to have a radius of 0 25cm and a comfortable viewing distance of 25cm the minimum separation between two objects that human eye can resolve at 500 nm wavelength is Question Type Single Correct Type 1 2 3 100 m 300 m 1 m

What should be the maximum angle of acceptance at the air core interface of an optical fibre if n and n are the refractive indices of the core an the cladding respectively sin 1 12 3 tan 2 2 1 sin 2 sin n n 4 sin n 12

surfaces A small air bubble is at the centre of a glass sphere of radii 5 cm When it is viewed from outside what will be the position of image Refractive index of glass is 1 5 1 At the same place as that of object 2 10 cm cm from the surface near the eye 3 18 3 7 5 cm from the surface of sphere near the eye

A glass 2 cube of edge length 5 cm placed on horizontal surface has a point source of light S placed at centre of face What should be minimum area to be covered on side faces so that no direct light comes out of the side faces 1 50 cm 3 100 cm S 2 39 25 cm or 4 80 cm S

A right angled glass prism u 3 is kept on a horizontal surface in contact with a vertical plane mirror as shown A ray of light travelling horizontally retraces its path when transparent liquid of refractive index u is filled in the space between prism and mirror Refractive index u of the liquid is 6 1 2 5 6 45 45 2 5 3 4 F

Two identical thin lenses are kept one beside other or optical axis as shown in the figure The right surface right lens is silvered focal length each lense is 20 radius of the silvered surface is 2 cm the focal leng combined system is Consider

49 A telescope whose objective lens has an aperture of 1mm for the wavelength of light 500A then limit of resolution of the telescope is 1 2 1 x 104 rad 3 5 1 x 104 rad 2 4 1 104 rad 4 6 1 x 10 rad 50 A ray of light is incident on a glass plate at the polarising angle 57 Then Given tan57

Consider the situation shown in figure The elevator is going up with an acceleration of 2 00 m s and the focal length of the mirror is 12 0 cm All the surfaces are smooth and the pulley is light The mass pulley system is released from rest with respect to the elevator at t 0 when the distance of B from the mirror is 42 0 cm Find the distance between the image of the block B and the mirror at t 0 200 s Take g 10 m s Distance is given in cm A M B a 2 00 m s 2

1 u 1 5 3 R 10 cm What is focal length of this curved surface Question Type Single Correct Type 1 2 3 4 10 cm 5 cm 20 cm 30 cm

The diameter of the objective lens of a telescope is 5 0 m and wavelength of light is 6000A The limit of resolution of this telescope will be 1 3600 1 0 03 2 3 03 3 0 06 4 0 15

19 An object is placed at 15 cm from a convex ler of focal length 10 cm At what distance from ler another convex mirror of radius 12 cm be place such that final image will coincide with object 1 18cm 3 14cm 2 17cm 4 20cm

99 At what angle a ray of light should incident on face AB so that it retraces it s path after reflection from question vered face AC 1 30 3 60 B 301 H 2 45 4 90

The plane face of a Plano convex lens of glass 3 2 having focal length 20 cm is silvered What type of mirror will it become and of what focal length f 1 Convex f 20cm 2 Concave f 20cm 3 Convex f 10cm 4 Concave f 10cm

3 Zero 4 Infinite 08 One of the refracting surfaces of a prism of angle 30 is silvered A ray of light incident at certain angle retraces its path If the refractive index of the material of the prism is 3 the angle of incidence of the ray is 1 30 2 45 4 22 10 3 60