Geometrical Optics Questions and Answers

Consider the compound lens optical system below with a 1cm object ho 20cm in front of lens 1 Lens 1 has focal length f1 2cm and lens 2 has focal length f2 5cm The focus on the right side of lens1 is placed on the left focus of lens2 A real image is formed on the right of lens 2 as shown object Bunda lens 1 lensz P 20cm fr fine image a Find q1 distance from lens 1 to the image formed by lens 1 b Find p2 the distance from lens 2 where the object is seen by lens 2 c Find q2 the distance from lens2 where the final image is formed d Find m the magnification of the system e Draw 2 rays that start from the object and converge on the final image opteca axis

32 A sphere has its right half polished so as to act as a mirror A paraxial light ray is incident from left reflects parallel to the incident ray as shown The refractive index of the material of the sphere is 1 2 2 1 8

2 A point light source is located at a distance L from a screen A thin converging lens of focal length f L 4 and aperture radius R held parallel to the screen makes a circular spot of light on the screen If lens is moved from the source towards the screen size of the spot varies Find the radius of the smallest light spot which can be obtained in this way on the screen R 2 FL L

A person can see distinctly up to a distance of 2 m an no further To see distinctly up to a long distance wh type of spectacles should he use What will be th power of the lens of the spectacles

A short sighted person can see distinctly the object sit uated at a distance of 20 cm from him What type of lens will he use to see the objects situated at a distance of 100 cm from him What will be the power of the lens

a person with spectacles of power 3 m 1 can see di tinctly the letters of newspaper placed at a distance o 25 cm from the eye At what distance should the news paper be kept to be able to read it without spectacles

A short sighted person can read a book only up to 15 cm from his eyes To read a book placed at a distance of 25 cm from him what type of spectacles should he use What will be the power of the specta cles

1 A telescope produces images of far object near to eye 2 A telescope produces images of far object magnified 3 A microscope produces images of near object magnified 4 A microscope produces image of near object far from eye

A person using spectacles having power 2 5 m 1 can see the objects distinctly at a distance of 25 cm What is the near point for the person What type of defect of vision does the eye have pertandinetan elicamentelovedlocoteste

A ray of light in air is incident on a glass plate at polarising angle of incidence It suffers a deviation of 22 on entering glass The angle of polarisation is a 0 b 68 c 56 d 90

L A ray of light in air is incident on a glass plate at polarising angle of incidence It suffers a deviation of 22 on entering glass The angle of polarisation is a 0 b 68 c 56 of a flint glass block 1 16 The d 90

A ray of light passes from vacuum into a medium of refractive index n If the angle of incidence is twice the angle of refraction then the angle of incidence is b sin n 2 a cos n 2 c 2cos n 2 d 2sin n 2

The magnifications for two positions of image of the same lens are 3 and 2 of a fix point object on a fix screen when the distance between the two positions of lens is 30 cm The focal lengths of the lens is

In a modified YDSE monochromatic uniform and parallel beam of light of wavelength 6000A and intensity W m is incident normally on two circular apertures A and B of radii 1 mm and 10 1 T 2 mm respectively Find the ratio of the intensity of the two sources

A liquid of refractive index 1 62 is placed in between two identical plano convex lenses as shown in figure A and B If refractive index of material of lens is 1 52 and FA FB are the focal length of combination in arrangement A and B respectively then 1 62 BFAR D959 ggddaa dut ez Ga uf 4 qqef ci guadaim 1 52 am FA FB B FA A A D FB B FA O Your Answer

8 An equiconcave diverging lens of focal length F is cut into two equal halves The two halves are turned around and joined with some liquid between them The lens obtained is converging with focal length F If the refractive index of the liquid is 3 then what is the refractive index of the lens 1 4 3 5 2 2 4 1 5 10 Weakon Rena d why not apple

A lens of diameter 5 0 cm and focal length f 20 0 cm was cut along the diameter into two identical halves In the process a thin layer of lens a 1 0 mm is lost Then the halves were put together to form a composite lens A source slit is placed 10 cm from the lens emitting light of wavelength 600 nm Behind the lens a screen wall located at a distance b 80 cm from lens Find the fringe width B 0 3 mm A 0 15 mm D 1 2 m C 0 6 mm

A point object O is placed at distance of 30 cm from a convex lens of focal length 15 cm as shown in the figure At what distance x from the lens should a convex mirror of focal length 40 cm be placed such that final image coincides with the object Al X 18 cm 30 cm 22 cm

The difference in the number of waves when yellow light propagates through air and vacuum columns of th same thickness is one The thickness of the air column is mm Refractive index of air 1 0003 waveleng mathongo mathongo mathongo mathongo mathongo mathor of yellow light in vacuum 6000 mathongo mathongo mathongo mathongo mathongo mathon

A lens of focal length f 40 cm is cut along the diameter into two equal halves In this process a layer of thickness 1mm is lost then halves are put together to form a composite lens In between focal plane and the composite lens a narrow slit is placed very close to the focal plane f The slit is emitting monochromatic light of wavelength 0 6um Behind the lens a screen is located at a distance L 0 5m from it as shown A B C Fringe width is 0 12 mm Fringe width is 0 24 mm Length of interference pattern is 1 8 cm S f 40cm Tu 0 5m

With regards to a telescope whi statement is incorrect NCERT Pg 34 1 Telescope is used to provide angu magnification of distant objects 2 Telescope has objective lens of lar power 3 Final image of refracting telescope inverted 4 With larger diameter of objective faim objects can be observed

OSH ershock to In the diagram the arrow is a real object of length 0 1 cm What is the size of the image obtained after the light rays pass through the lens The lens is equiconvex with R 5cm A 0 2 cm 0 1cm 2 10cm 1 B 0 05 cm 10cm 1 R 5cm The refractive index of the lens is 1 5 C 0 15 cm D None

4 3 A pile 4 m high stands in the lake such that it appears 1 m above the surface of water if refractive index of water is and sun rays make an angle of 450 with the water surface then length of the shadow of pile on the bed of the lake will be

R R 2 The minimum required size of plane mirror to visualize complete image of an object is Half of size of object 2 Is same as size of object 3 Depends on distance of object only 4 Depends on the ratio of distance of object and observer from plane mirror Puntor then

If s us and we are refractive indices of A B and C respectively such that a c total internal reflection can take when a ray of light travels from 1 C to A 3 B to A NCERT Pg 2 C to B 4 B to C

16 A prism has prism angle of 60 and its absolute refractive index is 1 76 The prism is dipped in a transparent liquid of refractive index x If the angle of minimum deviation is found to 46 in liquid what is x NCERT Pg 331 1 1 1 3 1 4 2 1 3 4 1 5

15 A simple magnifier has converging lens of focal length 2 5 cm What is its linear magnification for the image formed at near point NCERT Pg 341 1 6 3 11 2 9 11T2 4 16

A ray of light is incident from a denser to rarer medium The critical angle for total internal reflection is 8c and the Brewster s angle of incidence is 8 such that sinc sin0 n 1 28 The relative refractive index of the two media is A B C skipped D 0 2 0 4 0 8 0 9 G M

A glass slab of thickness 4 cm contains the same number of waves as 5 cm of water When both are traversed by the same monochromatic light If the refractive index of water is 4 3 What is that of glass A skipped B C D 5 3 5 4 16 15 1 5 G

In an experiment a plane wave passing through a medium represented by E z t Eg sin 4 5x10 7 3 10 4 5 10 i The refractive index of the medium at this frequency will be A B C D 1 41 1 33 0 86 2 0 X

4 5 3 Cylindrical 4 Both 1 Wave fronts associated with point sources are 1 Cylindrical 2 Spherical 3 Planar 4 Both 1 and 3 The value of angle r in figure is Symbols have the usual meanings Rarer medium air Denser medium MIN Incident wavefront 37 153 Refracted wavefront

4 1 1 GO0082 ng power 8 apart The 89 GO0088 The focal lengths of the objective and eye piece of a telescope are respectively 100 cm and 2 cm The moon subtends an angle of 0 5 at the eye If it is looked through the telescope the angle subtended by the moon s image will be 1 100 2 50 3 25 4 10

Qs When the object is placed at a distance of 3 2 focal lengths from a convex mirror the type of image formed in O A Erect and real O B Inverted and virtual O c Erect and virtual O D Inverted and real

of focal length 97 cal length 2cm 50 meter tall at is the height by the objective Pre Medical Physics 61 A myopic person can not see objects lying beyond 2 m The focal length and power of the lens required to remove this defect will be 1 1 m 0 5 D 3 0 5 m 0 5 D 2 2 m 0 5 D 4 0 5 m 0 5 D

A beam of light from a source is incident normally on a plane mirror fixed at a distance 2m from the source The beam reflected back as a spot on a scale placed just above the source When the mirror is rotated through a small ang 1 8 the spot of the light is found to move through a distance d on the scale The distance d is A B 0 1831 m 0 1256 m 3 14 m None of these

60 80 Pre Medical Physics Two lenses of focal length 10 cm and 15 cm when put in contact behave like a convex lens They will have zero longitudinal chromatic aberration if their dispersive powers are in the ratio 1 3 2 121 2 3 3 3 2 1 2 3

2 Let the xz plane be the boundary two transparent media between Medium 1 in z 20 has a refractive index of 2 and medium 2 with z 0 has a refractive index of 3 A ray of light in medium 1 given by the vector A 6 3 1 8 3 1 10 k is incident on the plane of separation The angle of refraction in medium 2 is a 45 c 75 b 60 d 30

7 In figure ABC is the cross section of a right angled and ACDE is the cross section of a glass slab The value of 0 so that light incident normally on the face AB does not cross the face AC is given sin 3 5 37 A E gas bau ghint Outenique et posizo brad mus odi mo 1 0 37 O B 0 n 6 5 C D 2 0 37

6 A spherical surface of radius of curvature R separates air refractive index 1 0 from glass refractive index 1 5 The centre of curvature is in glass A point object P placed in air is found to have a real image Q in the glass The line PQ cuts the surface at a point O and PO OQ The distance PO is equal to 1 R 2 3 R 3 2 R 4 5 R

GO0051 52 Three prisms 1 2 and 3 have the prism angle A 60 but their refractive indices are respectively 1 4 1 5 and 1 6 lf 8 82 8 be their respective angles of deviation then 1 8 8 8 3 8 8 8 2 8 8 8 4 8 8 8

sm GO0050 to th 51 For a prism graph between angle of deviation 8 and angle of incidence will be 14 ex 52 9 15 DW 18 34 he 1 0 3 2 GO0051

GO0029 0 When a ray of light enters a medium of refractive index it is observed that the angle of refraction is half of the angle of incidence is than angle of incidence is 1 2 cos 2 3 2 cos 2 cos 2 4 2 sin 1 2 C00030 37

GO0048 54 The refractive index of the material of a prism is 2 and its refracting angle is 30 One of the refracting surfaces of the prism is silvered A beam of monochromatic light entering the prism from the other face will retrace its path after reflection from the silvered surface if its angle of incidence on the prism is 1 60 2 0 silvered ce 2A on path after surface mis G00049 3 30 4 45 GO0054

GO0045 6 If the refractive indices of crown glass for red yellow and violet colours are 1 5140 1 5170 and 1 5318 respectively and for flint glass these are 1 6434 1 6499 and 1 6852 respectively then the dispersive powers for crown and flint glass are respectively 1 0 034 and 0 064 3 1 00 and 0 064 2 0 064 and 0 034 4 0 034 and 1 0

31 White light is incident on the interface of glass and air as shown in the figure If green light is just 38 totally internally reflected then the emerging ray in air contains 1 Yellow orange red 2 Violet indigo blue 3 All colours 4 All colours except green Air Glass White Green 39

4 A ray of light passes through equilateral Prism u 1 5 such that angle of incidence is equal to angle of emergence and the later is equal to 3 4th of Prism angle The angle of deviation is 1 60 2 30 3 45 4 120

8 The angle of minimum deviation measured with a prism is 30 and the angle of prism is 60 The refractive index of prism material is 1 2 2 2 3 Z NI 4 4 3

A 20 cm high object is placed on the principal axis of a concave mirror at a distance of 12 cm from the pole If the image is inverted real and 50 cm high find the location of the image and the focal length of the mirror

Q6 Two coins are placed one is under 35 cm of water other 35 cm of glass The coins are at equal distances from your eye Which one appears closer to your eye O A Both appear at same distance B Coin under water c Coin under glass D Cannot see the image of coin

Q3 A light beam converges to a point P A lens is placed in the path of convergent beam at a distance of 12 cm from P If the lens is a concave lens of focal length 16 cm the point at which beam converges is O A 48 00 cm B 24 00 cm c 24 00 cm D 48 00 cm Mar