Geometrical Optics Questions and Answers

20 A ray of light starting from air passes through medium A of refractive index 1 50 enters medium B of refractive index 1 33 and finally enters medium C of refractive index 2 42 If this ray emerges out in air from C then for which of the following pairs of media the bending of light is least a air A c B C b A B d 813 C air

Refracting angle of the prism op see figure is 30 and is kept in air The angle of incidence of the beam on the face of the prism a 37 Determine the angle of deviation 8 in degree of the ray from the original direction after passing through the prism The refractive index of the material of the prism n 1 2 4

Consider the following statements and choose the incorrect one A ray which is parallel and close to the principal axis of a concave mirror goes through the focus of the mirror after reflection For an incident ray which passes through the O center of curvature of a concave mirror retraces its path after reflection For rays which are incident on a spherical O mirror at an angle greater than 5 laws of reflection are not valid For a ray passing through or directed towards the focus of the concave mirror or appearing to pass through or directed towards the focus of a convex mirror the reflected ray is parallel to the principal axis

1 In the diagram given below X and Y are the end colours of the spectrum of white light The colour of Y represents the White light La a Colour of sky as seen from earth during the day b Colour of the sky as seen from the moon c Colour used to paint the danger signals d Colour of sun at the time of noon

An equi convex lens has focal length equal to 20 cm If the lens is cut in two equal halves by a plane perpendicular to the principal axis then the new focal length of any one half will be O 10 cm 20 cm 40 cm 60 cm

In the figure shown consider the first reflection at the plane mirror and second at the convex mirror AB is object R 120cm B H 10cm 10cm 50cm A the second image is real and inverted with magnification 1 5 B the second image is virtual and erect with magnification 1 5 C the second image moves towards the convex mirror D the second image moves away from the convex mirror

Light takes 8 minutes 20 second to reach from sun to the earth If the whole universe and atmosphere is hypothetically filled up with a liquid of refractive index 1 5 then the time taken by the light will be 8 minutes 10 minutes 12 minutes 30 sec 20 minutes

A compound microscope is an instrument which consists of two lenses L and L The lens L called objective forms a real inverted and magnified image of the given object This serves as the object for the second lens L the eye piece The eye piece functions like a simple microscope or magnifier It produces the final image which is inverted with respect to the original object enlarged and virtual 57 What types of lenses must be L and L a Both concave b Both convex c L concave and L convex d L convex and L concave 58 What is the value and sign of magnification according to the new Cartesian sign convention of the image formed by L Value Less than 1 and Sign Positive Value More than 1 and Sign Positive Value Less than 1 and Sign Negative d Value More than 1 and Sign Negative a b c 59 What is the value and sign of according to new convention magnification of the image formed by L b c d Value Less than 1 and Sign Positive Value More than 1 and Sign Positive Value Less than 1 and Sign Negative Value More than 1 and Sign Negative F Cartesian sign 30 If power of the eyepiece L is 5 diopters and it forms an image at a distance of 80 cm from its optical centre at what distance should the object be b 16 cm d 20 cm c 18 cm a 12 cm

A object is placed at Centre of Curvatur e concave mirror which of the following statement is not true in reference to the diagram shown above Image formed is real Image formed is enlarged Image is formed at a distance equal to the double the focal length

Water has a refractive index of 4 3 At what angle of incidence should a ray be incident on water air interface from water to suffer total internal reflection sin 4 5 O sin 4 7 O sin 3 4 O sin 3 5

A magician during one of his shows makes a lens disappear by immersing it in a liquid of refractive index 1 5 The refractive index of the material of the lens will be 1 1 02 1 1 5 O 1 9

Q 36 A glass slab of thickness 2 5 cm having refractive index 5 3 is kept on an ink spot A transparent beaker of very thin bottom containing water of refractive index 4 3 up to 8 cm is kept on the glass block Calculate apparent depth of the ink spot when seen from the outside air

45 An object is placed at a distance of 30 cm from a convex lens the magnification produced is 1 which is real and inverted The focal length 2 of lens is 1 30 cm 3 15 cm Ans 2 2 10 cm 4 can t be determined

An object was placed upright 25 cm in front of a converging lens of focal length 20 cm A concave mirror with a focal length of 15 cm was placed 120 cm behind the lens Which of these describes the final image ga 20 cm MEER 120 cm ar A Real enlarged af a Correct Answer B Virtual upright 15 cm Your Answer M 25 O G B af

When a ray of light passes through a glass prism it suffers two refractions During these refractions the ray bends a Away from the base in both cases t Towards the base in both cases c Towards the base in first case and away from the base in second case d Away from the base in first case and towards the h b

The power of a combination of two lenses in contact is 1 0 D If the focal length of one of the lenses of the combination is 20 0 cm the focal length of the other lens would be a 120 0 cm b 80 0 cm M d 20 0 cm 25 0 cm

7 A person has near point at 60 cm The focal length of spectacles lenses to read at 22 cm having glasses separated 2 cm from the eyes is Xov 2017 Gujarat a 40 cm c 20 cm b 10 cm d 30 cm width 28

a There is a point object placed in front of a pla mirror If the mirror is displaced by 10cm away f the object find the distance by which image will displaced 1 10cm 3 15cm 2 5cm 4 20cm

A converging lens shown in the sketch has focal length of 5 cm An object 1 cm tall is placed 4 cm from the lens The image of the object is F O None in the list 20 cm from the lens and is virtual 1 20 cm from the lens and is real 20 cm from the lens and is real 1 20 cm from the lens and is virtual F

A beam of diameter d is incident on a glass hemisphere as shown If the radius of curvature of the hemisphere is very large in comparison to d then the diameter of the beam at the base of the hemisphere will be d 3 2 1 Ans 2 3d

A point object is placed at a distance of 60 cm from a convex lens of focal length 30 cm If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it the final image would be formed at a distance of 60 cm 40 cm 1 30 cm from the plane mirror it would be a virtual image 2 20 cm from the plane mirror it would be a virtual image 3 20 cm from the lens it would be a real image

21 An optical element is shown in surfaces are 10 cm and 20 cm Calculate distance between two spherical surfaces so that image of the object coincides with the object itself R 10 cm H 30 cm 1 100 cm 3 110 cm 3 2 d R 20 cm 2 80 cm 4 95 cm

Focal lengths of objective and eyepiece of Gallilian telescope have magnitudes of 100 cm and 5 cm respectively In normal adjustment the distance between the objective and eyepiece is 2 100 cm 4 90 cm 1 105 cm 3 95 cm

A convex lens is kept between the object and screen kept 40 cm Now a glass block of 6 cm thickness is placed in contact with the light source To get the sharp image again the screen is shifted by a distance d cm away from the lens then Find the value of d

A ray of light travelling from medium A to medium B is shown in figure Refractive index of medium B with respect to medium A is O 3 2 O 1 451 60 Medium B Medium A

A small object is placed 10 cm infront of a plane mirror If you stand behind the object 30 cm from the mirror and look at its image the distance focused by your eye will be 40 cm O 80 cm O 60 cm O 20 cm Marks 4 1

Thank you 15 Which of the following quantities related to a does not depend on the wavelength of the ind light 1 Refractive index 2 Focal length 3 Power

01 28 25 A glass beaker has diameter 4cm wide at the bottom An observer observes the edge of bottom when beaker is empty as shown in figure When the beaker is completely filled with liquid of refractive index 5 2 he can just see the centre of bottom then the height of glass beaker is O4 cm 16 cm O cm 200 O None of these Mark Physic 0 answ

Qn 11 A plane mirror of semicircular shape radius 1m is placed in y Z plane with its diameter along y axis and centre at origin An object is placed on the axis of mirror at point 5 0 0 At a distance of 10 m from plane mirror there is a wall also parallel to y z plane The ratio of area of spot of light on wall to that of mirror is Z r 1m Your Answer 1 Answer 9 0 5m A plane mirror of semicircular shape radius 1m is placed in v z plane with its diamete

A ray of light travels in different media as shown in the figure The emerging light grazes the boundary of air and water The value of g in terms of 0 is Air O cosece cosece cosec 6 Water 4 3 44 Glass H

2 There is a vessel containing a liquid of refractive index 1 4 A point source of light is situated at a depth of 5 cm from the surface of the liquid An opaque disc floats directly above the source of light If anyone looks downwards from any point on the surface of the liquid and if the point source of light is not visible what will be the minimum nito 9 radius of the disc 5 1 cm

An object having a length of 21 cm is placed away from the concave mirror of radius of curvature 10 cm A glass slab of refractive index 1 5 is placed perpendicular to the prin ciple axis Thickness of the glass plate is 3 cm Find out the final position of the last image Distance of the nearer end of the glass slab from the mirror is 1 cm No 8 16 cm from the mirror

For a concave mirror paraxial rays are focused at distance distance x from pole then R is radius of curvature R 2 1 X R 2 3 x 2 x f 4 R from pole and marginal rays are focused a 2 AI R

6 The diagram below shows two narrow converging lenses having length of focus a and a The horizontal separation between them is d The distance d is less than focal length of both lenses The displacement of D occurs between their centres as shown in the figure Following the cartesian system with the origin of coordinates O at the centre of the first lens the coordinates of the focal point of this lens system for rays coming from the left as shown in figure are given by 11111 A X a a d a d a a d a a d a a d D None of the above B X a a a a y D C x y D D a d a a d D a a

1 Figure shows three thin lenses of the same material with sides that either are flat or have same radius of curvature Rank the lenses according to the magnitude of focal length greatest first DOD Plano Convex Lens Double Convex Concavo Conver Leas Lens O Double convex concavo convex Plano convex O concavo convex Plano convex double convex O double convex Plano convex concavo convex Plano convex concavo convex double convex

View in English As shown in figure a convergent lens is placed inside a cell filled with liquid The sens hos focal length 20 cm when in air and its material has refractive index 150 if the liquid has refractive index 1 80 the focal length of the system is 0 2 Correct Anwer 4 80 cm 80 cm 24 cm 160 cm

A short straight object of height 100 cm lies before the central axis of a spherical mirror whose focal length has absolute value 40 cm The go image of object produced by the mirror is of height 25 cm and has the thonge same orientation of the object One may conclude from the information conge 1 Image is real same side of concave mirror ngemathongo 2 Image is virtual opposite side of convex mirror mathango 3 Image is virtual opposite side of concave mirror mathonga mathong 4 Image is real same side of convex mirror mathongo mathona mothongs

touches the rod Its magnification will be 1 1 2 2 3 3 4 4 An achromatic convergent doublet of two lenses 44 in contact has a power of 2D The convex lens has power 5D What is the ratio of the dispersive powers of the convergent and divergent lenses 1 2 5 3 5 2 2 3 5 4 5 3 Consider the following two statement A and B and 45 ara ya chatua 6 fin da 1 I 2 2 3 3 a grofa i de fund furent start a fa a 2D SD t 1 2 5 3 5 2 4 4 2 3 5 4 5 3 A fe te

A boy stands straight infront of a mirror at a distance of 30 cm aways from it He sees his erect image whose height is 1 5 th of his real height The mirror he is using is plane mirror convex mirror concave mirror

A thin lens of same radius of curvature 20 cm is having two different medium on its two sides extending upto infinity as shown in the figure Then BA B C D 14 1 3 4 31 It may behave as a converging lens of focal length 60cm It may behave as a diverging lens of focal length 60cm It may behave as a converging lens of focal length 80cm It may behave as a diverging lens of focal length 80cm

A ray of light from a denser medium is incident on a rarer medium at an angle 8 The reflected and refracted rays are at right angles to each other If r be the angle of refraction the critical angle for the pair of media is 1 tam sin 3 sin cos 2 sin tan 8 4 cos sin

9 A small object is placed 10 cm infront of a plane mirror If you stand behind the object 30 cm from the mirror and look at its image the distance focused by your eye will be 2 20cm 3 40 cm 1 60 cm 4 80 cm 0 If u represents the refractive index when a light ray goes from medium i to medium j then the

A point source is kept on the principal axis of a convex lens of focal length f at a distance 4f from it Behind the lens there is a concave mirror of focal length f There are two positions of mirror such that final image coincides with the point source If the ratio of the distance between lens and mirror for the two cases is find the value 2 of n

the objec A U shaped wire is placed before a concave mirror having radius of curvature 20 cm as shown in figure Find the total length of the image I 2cm 15cm

5 There are two plane mirror inclined at 40 as shown in the figure A ray of light is incident on mirror M then what should be the value of angle of incidence i so that the light ray retraces its path after strking the mirror M 1 40 2 50 40 M 3 60 M 4 70

Consider the setup shown in the figure which uses a right angled prism to transmit a horizontal incident ray This device is known as anamorphic de magnifier Through the prism the ray experiences total internal reflection TIR twice and then exits as shown in the figure The prism is made from a glass of refractive index u If the emerging ray propagates horizontally which of the following is a correct expression for refractive index h

When an object is placed at infinity of a con cave mirror then the image is of point size Then since we can t see it entirely then how do we know that it is real and inverted When an object is placed at the focus of a c oncave mirror then it s image is formed at i nfinity Since we can t capture it on a screen then how do we know that it is a real and inv erted image

Write an expression for unit vector along reflected ray 4 if unit vectors i and n represents unit vectors along incident light ray and normal at point of reflection and outward from surface respectively and angle between incident ray and normal ray

A convex lens of focal length 20 cm is cut into two equal parts that are shifted as shown in figure An object is placed at 30 cm from point C The distance between the images formed by the two halves of the lens is 0 30 cm C 14 cm

A Fish and a Fly Approaching Each Other A fish in an aquarium approaches the left wall at 2 5 m s observes a fly approaching it at 8 m s If the refractive index of water is 4 3 Find the actual velocity of fly com PAPAY