Optical Instruments Questions and Answers

A thin convergent lens of refractive index u has a power 5 D in air and 2 D in a liquid of refractive index 1 5 The refractive index of the material of the lens is equal to 2 25 O 1 2 3 75

A particle moves with a constant speed of 3 m s along the path shown in figure The acceleration of the particle at position x 1 5 m is y 3x 1 5 m a 0 24 0 03 m s b 0 61 0 03 m s X

A circular coil of radius R is revolving around a vertical wire PQ with a constant angular speed Magnetic field B is acting in to the paper plane Resistance per unit length of circular loop is 192 m whereas the resistance of PQ wire is R The magnitude of current in PQ wire when direction of magnetic field is along the plane of loop is at t 0 B is perpendicular to plane of loop BRO 14m 3 3 BRO 16n 3 52m 52m A B 60 C BRoo 16n 3 3 52m D BRO 9 3 6m 52n

9 The following diagram shows the use of an optical device to perform an experiment of light As per the arrangement shown the optical device is likely to be a 79 81 a Concave mirror c Convex mirror b Concave lens d Convex lens

b 20 cm length of a certain optically active solution causes right handed rotation of 40 and 30 cm of another solution causes left handed rotation of 24 What will be the optical rotation produced by 30 cm length of the mixture of the above solutions in volume ratio 1 2 It is given that the solutions do not react chemically

The reflective surface is given by y 2 sin x The reflec tive surface is facing positive axis What is the least value of coordinates of the point where a ray parallel to positive x axis becomes parallel to positive y axis after reflection a T c 2 3 b d 2 4

A point source of light S is placed at a distance L in front of the centre of a mirror of width d hangs on a wall A man walks infront of the mirror along a line parallel to the mirror at a distance 3 L from it as shown in figure Find the distance over which he can see the image of light source Question Type Single Correct Type 1 3 d 2 4 d Light source IH L 3L Man

A glass hemisphere of radius R and material having refractive index 1 5 is silvered on its flat face as shown in the figure A small object height h is located at a distance 2R from surface of hemisphere The final image will form O at a distance of R from silvered surface on right side on the hemispherical surface at the plane surface O at a distance of 2 R from the curved surface on left side 2R

What will be the height of image of an object of heigh 2 mm placed on the axis of convex mirror of radius of curvature 40 cm at a distance of 20 cm from convex mirror 20 mm 10 mm 6 mm 1 mm

D A convex mirror has a radius of curvature of 22 cm If an object is placed 14 cm away from the mirror then its image is formed at 1 6 2 cm on the front side of the mirror 2 6 2 cm on the back side of the mirror 3 51 3 cm on the front of the mirror 4 51 3 cm on the back side of the mirror GO002

Question No 16 White light is used to illuminate the two slits in a Young s double slit experiment The separation between slits is b and the screen is at a distance d b from the slits At a point on the screen directly in front of one of the slits certain wavelengths are missing Some of these missing wavelengths are Options b 2d 2b d b 3d 2h 3d

A toy plane has a siren installed on it The siren has a frequency of 100 Hz The plane is moving at a velocity of 160 m s in the horizontal direction Assume that vertically upward is y direction direction of motion of plane is x direction and plane is 8m above the ground The origin is vertically below the plane on the ground at a particular instant Speed of sound 320 m s A the frequency recorded by a recorder at 0 0 6m is 100 Hz B the frequency recorded by a recorder at 6 0 0 is Hz 500 3 C the frequency recorded by recorder at 8 0 4 is 150 Hz D the frequency recorded by recorder at 8 0 4 is 120 Hz

In the potentiometer circuit shown below balancing length AJ when switch S is closed and S is open is found to be 60 cm and that 4J when S is 1 2 closed and S is open is 80 cm The unknown resistance X then is 1 A AJ 60 cm AJ 80 cm 30 2 www E 4 S O www X B

An optical component and an object S placed along its optic axis are given in Column I The distance between the object and the component can be varied The properties of images are given in Column II Match all the properties of images from Column II with the appropriate components given in Column I Indicate your answer by darkening the appropriate bubbles of the 4 x 4 matrix given in the ORS Column I A B C D YPY p 9 r A n gr s B a 0 n ar s D p q r s Column II Real image Virtual image Magnified image Image at infinity

short linear object of lengties along the axis of a concave mirror of focal length f at a distance u from the pole of the mirror The size of the image is equal to 1 f 2 1 L U F f 2 L f 2 u f 2

2 34 Two thin convex lenses each of focal length 20 cm are placed in contact coaxially If a point object is placed at a distance of 20 cm from the lens combination then the image formed from the combination is at a distance of 1 10 cm 3 30 cm 2 20 cm 4 Infinity

View in question No 10 beam of light of wavelength 6000 A falls on a narrow slit and the diffraction pattern is observed at a screen 3 m away from the slit If the slit width is 0 9 mm then the position of the first order mine Central maximum is O 4mm 3 mm 1 mm O2 mm

An oil layer that is 5 0 cm thick is spread smoothly and evenly over the surface of water on a windless day What is the angle of refraction in the water for a ray of light that has an angle of incidence of 40 as it enter the oil from the air above The index of refraction for the oil is 1 15 and for water it is 1 33 32 27 29 39

ALLEN A person cannot see objects clearly beyond 2 0 39 m The power of lens required to correct his vision will be 1 2 0 D 3 1 0 D 2 1 0 D 4 0 5 D aft 2 0 m fra at it and e antent and for starzen Afg 1 2 0 D 3 1 0 D 2 1 0 D 4 0 5 D

ALLEN Refractive index of violet yellow and Red colour 14 of light for a material of lens are 1 66 1 64 1 62 respectively If mean focal length of lens is 10cm Then chromatic abberation between the colour of violet and red will be 1 0 625 cm 2 0 125 m 3 0 02 cm 4 0 cm 1 66 1 62 1 meg d su z 1 faqe m 1 0 625 cm 3 0 02 cm of 2 0 125 m 4 0 cm

A prism shaped imaginary structure is given A point charge is kept as given in figure Calculate electric flux passing through the prism q 1 4 0 a 45 q 19 2 8E0 q

A monochromatic light ray is incident at an angle 60 to a face of a transparent trihedral prism hav ing a refractive index of 3 Having undergone double refraction the ray emerges in a direction normal to this face Angle of prism is 1 37 2 30 3 45 4 60

A ray falls on a prism ABC AB BC and travels as shown in figure The minimum refractive index of the prism material should be 1 3 2 2 3 A uestion Type Single Correct Type 1 5 90 B 90 C

Let a b and a2 b be the unordered pair of natural numbers such that the difference of their sum and their product is equal to the sum of their LCM least common multiple and GCD greatest common divisors Find the value of a b a b

3 Part of a light ray striking an interface between air and water is refracted and part is reflected as shown The index of refraction of air is 1 00 and the index of refraction of water is 1 33 The frequency of the light ray is 7 85 x 10 6 Hz a If 8 measures 40 find the value of 0 b If 8 measures 40 find the value of 03 c Calculate the speed of the light ray in the water d Calculate the wavelength of the light ray in the water e What is the largest value of 8 that will result in a refracted ray Air Water 1 83

A disc revolves with speed of 0 4 revolutions per second and has radius of 15 cm Two coins are placed at 4 cm and 14 cm away from the centre of the disc If the coefficient of friction between coins and the disc is 0 15 then Coin at 4 cm from centre will slip Coin at 14 cm from centre will slip Both coins at 4 cm and 14 cm from centre slip No coin will slip

Consider a transparent hemisphere of refractive index 2 in front of which a small object is placed in ai n 1 as shown F 17 For what value of x the final image of object at O be virtual A 2R B 3R RN 1 4 R C 2 2 2 D 1 5 R

In a compound microscope the focal length of two lenses are 1 5 cm and 6 25 cm If an object is placed at 2 cm from objective and the final image is formed at 25 cm from eye lens the distance between two lenses is uestion Type Single Correct Type 1 2 3 6 00 cm 7 75 cm 9 25 cm 11 0 cm 15 49 B View Solution UT17 our Answer 2 Status Incorrect BOUND OVERVIEW PERFORMANCE LEADERBOARD All Poyales Leader English E A simple microscope has a focal length of 5 cm The magnification at the least distance of distinct vision is Question Type Single Correct Type 1 5

Light is passing from air into a liquid and is deviated 19 when the angle of incidence is 52 Under what conditions will total internal reflection occur at this interface A 53 7 B 43 7 C 63 7 D 23 7 AL

18 A solenoid 50cm long has 4 layers of winding of 350 turns each If the current is 6A then magnetic field at the centre of solenoid is 1 5 3x10 3 T 3 3 1 10 4 T 2 2 1 10 T 4 4 1 10 T You

The speed of electrons in a scanning electron microscope is 1x107 ms 1 If the protons having the same speed are used instead of electrons then the resolving power of scanning proton microscope will be changed by a factor of 2 3 1837 1 1837 1 1837

Radius of concave mirror is 30 cm and size of image real is twice as that of object then the object distance from the mirror is 1 15 cm 3 22 5 cm 2 30 cm 4 45 cm tures 20 cm an

Only one correct answer A A plane mirror always forms a virtual image B C D The virtual image formed by a concave mirror is always enlarged The critical angle is always defined in the denser medium A glass slab cannot deviate the light

Two closely located monochromatic coherent sources create a fixed interference pattern on a screen The frequency of one of the sources is then decreased What will happen to the interference pattern as a result 1 The pattern will completely disappear 2 The fringe spacing will increase 3 The fringes will shift up or down but the spacing will remain constant 4 The fringe spacing will decrease

22 A carrot looks orange in colour because of the carotene molecule in it This means that the carotene molecule absorbs light of wavelengths a longer than 550 nm b shorter than 550 nm Vc longer than 700 nm d shorter than 700 nm

mothon mat Given below are two statements One is labeled as Assertion A and the other is labeled as Reason R Assertion A For a simple microscope the angular size of the object equals the angular size of the image Reason R Magnification is achieved as the small object can be kept much closer to the eye than 25 cm and hence it subtends a large angle In the lig of the above statements choose the most appropriate answer from the options given below athango mathor 1 Both A and R are true but R is NOT the correct explanationof A 2 Both A and R are true and R is the correct explanation of A mathongo mathongo mathos 3 A is true but R is false 4 A is false but R is true thangamathongo mathongo mathongs mathon

A point source of light S placed at a distance 60 cm infront of the centre of plane mirror of width 50 cm hangs vertica on a wall A man walks infront of the mirror along a line parallel to the mirror at a distance 1 2 m from it see in the figure The distance between the extreme points where he can see the image of the light source in the mirror is em mathongo athongo mathongo mathongo mathongo mothongo matho mahoo 50cm 9 mathonge mathanga 60cm S mathango mathongo Amathongo mohoo W mathongo mathongo mathongo mathongo matho

focal length of a biconvex lens made of glass of equal radii is f If the lens is dipped in he water then the focal length becomes 3 4 Take refractive index of glass and water as and respectively 2 3 Options 1 2 3 2f 4f 5 3 f 7 4 f

In an experiment with Michelson interferometer the distance travelled by the movable mirror is 0 2945 mm for obtaining two successive positions of maximum

Why doesnt the use of convex lens for hype rmetropia affect the distant or far vision of a person Why doesnt the use of concave lens for my opia affect the near vision of a person f juot goto YOU roigot

Find by construction the optical centre of a lens and its main foci on the given optical axis N N if the positions of the source S and the image S are known Fig 1 42 a N S a N N S Fig 1 42 S b N

Four trials of Young s double slit experiment are conducted 1 Given blue 450 nm and red 700 nm i In the first trial blue light passes through two fine slits 400 m apart and forms an interference pattern on a screen 4m away ii In a second trial red light passes through the same slits and falls on the same screen iii A third trial is performed with red light and the same screen but with slits 800 m apart iv A final trial is performed with red light slits 800 m apart and a screen 8m away IV f angle between the first maxima and central maxima in each trial is 0 0 0 0 respectively istance between the central maxima and first maxima is y y y y respectively then A 0 0 0 0 11 IV CAZA A A B y y Y Y N 11 D y y y y

A ray of monochromatic light is incident on one refracting face of a prism of angle 75 It passes through the prism and is incident on the other face at the critical angle If the refractive index of the material of the prism is 2 the angle of incidence on the first face of the prism is a 30 b 45 c 60 d None of these

6 A slab of material of refractive index 2 shown in figu has a curved surface APB of radius of curvature 10 cm an a plane surface CD On the left of APB is air and on th right of CD is water with refractive indices as given in th figure An object O is placed at a distance of 15 cm from th pole P as shown The distance of the final image of O from P in cm as viewed from the left is n 1 0 P B n 2 0 15 cm 0 C M E D 4

2 Two plane mirrors AB and AC are inclined at an angle 0 20 to each other A ray of light starting from point P is incident at point Q on the mirror AB then at R on mirror AC and again on S on AB Finally the ray ST goes parallel to mirror AC The angle i which the ray PQ makes with the normal at point Q on the mirror AB is 1 20 3 40 SB R BT 2 30 4 60

Diameter of the moon is 3 5 10 km and its distance from earth is 3 8 x 105 km It is seen by a telescope whose objective and eyepiece have focal length 4 m and 10 cm What will the angular diameter of the image of the moon Question Type Single Correct Type 1 2 3 4 0 36 radian 0 20 radian 0 46 radian 0 50 radian

a A prism having material of the medium P deviates blue light through an angle of 16 and a red light through an angle 10 Another prism having material of the medium Q deviates the blue light through an angle of 14 and the red light through an angle 8 Which material has greater dispersive power I Q has greater dispersive powerl

0 P is a small angled prism of angle 3 made from material of refractive index 1 2 A ray of light is incident on it as shown in figure The angle of deviation for the rays refracted from prism is NCERT Pg 331 1 2 3 0 8 90 3 Glass 2 3 4 0 6

A compound microscope consists of objective lens of focal length 1 cm and eye piece with focal length of 2 0 cm a tube has length 20 cm What is magnification NCERT Pg 3 1 100 3 220 2 200 4 250

3 A small pin fixed on table top is viewed from above from a distance of 40 cm By what distance would pin appear to be raised if viewed from the same point through a 12 cm thick glass slab held parallel to the table Refractive index of glass is 1 5 NCERT Pg 345 1 4 cm 2 5 cm 3 6 cm 4 8 cm