Optical Instruments Questions and Answers

Where should an object be placed in front of concave mir ror of focal length 15cm to have magnification of 3 sir why it is taken as 3 Where should an object be placed in front of a concave mirror of focal length 15 cm to have a magnification of 3 in case of a real image b virtual image

3 2 cm 4 13 cm 3 The magnifying power of a microscope with an objective of 5 mm focal length is 400 The length of its tube is 20 cm The focal length of eye piece is final image formed at infinity 1 200 cm 2 150 cm

3 A real image of half the size of the object is produced by a spherical mirror On moving the object away from the mirror by 0 30 m the size of the image becomes that of the object Calculate the radius of curvature of spherical mirror Ang

posit charged When light travels from glass to air the incident angle is 0 and the refracted angle is 0 Then the correct relation between two angles is 1 0 0 2 0 0 3 0 0 4 Not predictable

concave mirror is producing a virtual image of the object Which of the following statement is incorrect A The linear magnification is always greater than one Except at the pole B The linear magnification is always less than one c The magnification tends to one as the object move nearer to the pole of the mirror D The distance of the object from the pole of the mirror is less than the focal length of mirror

Question 11 An object is moving parallel to the principal axis of a concave mirror at some height as shown in the figure For the given location of the object and image the direction of motion of image will be directed along object image DA St line I B St line 2 c St line 3 D St line 4

If the focal length of the lens is 20 cm A virtual object lies 12cm behind the mirror as shown in the following figure The distance of the image from lens in the is 15 n cm Find n 12 cm

23 A point object on the principal axis at a distance 15 cm in front of a concave mirror of radius of curvature 20 cm has velocity 2 mm s perpendicular to the principal axis The velocity of image at that instant will be A 2 mm s C 8 mm s B 4 mm s D none of these

In a terrestrial telescope the focal length of objective is 90 cm of inverting lens is 5 em and of eyepiece is 6 cm If the final image is at 30 cm then the magnification will be 1 21 3 18 2 12 4 15

An object is moving towards a concave mirror a focal length 24 cm When it is at a distance of 6 cm from the lens its speed is 9 cm s the speed c its image at that instant is 1 4 cm s towards the mirror 2 9 cm s towards the mirror 3 4 cm s away from the mirror 9 cm s away from the mirror

Find the focal length of the lens shown in the figure The radii of curvature of both the surfaces are equal to R H H H 1 2 3 H3 H1 143 R H R H3 H1 H3R H3 H1 R 1 11 R R

Chlead get the famed lloy yo go i fanfte affari Deduce expression for the equivalent focal length of two thin lenses in contact and obtain an expression fo the focal length of a combination of two coaxial thin lenses separated by some distance Caled stel dan PIATHT

4del 4991004 fight Gel 09 fufe affery la gio ac i Deduce expression for the equivalent focal length of two thin lenses in contact and obtain an expression for the focal length of a combination of two coaxial thin lenses separated by some distance

34 In case product of magnification in both cases is 1 1 2 2 3 Zero 4 Infinite In the displacement method a convex lens is placed in between an object and a screen If the magnifications in the two positions are m and m and the displacement of the lens between the two positions is x then the focal length of the lens is 1 X m m X 3 m m 2 X m m X 4 m m ough a Prism 39 An isosceles prism of angle A 30 has on surfaces silvered Light rays falling at an incidence 60 on the other surface retrace after reflection from the silvered surface The index of prism material is 36 The focal length of a planoconvex glass lens is 20 cm g 1 5 The plane face of it is silvered An illuminating object is placed at a distance of its axis along the convex 40 60 30 2 1 5 1 1 414 3 1 732 A plot between the angle of d incidence is shown in figure can say that the prism ang

The magnifications produced by a convex lens for two different positions of an object are m and m respectively m m If d is the distance of separation between the two positions of the object then the focal length of the lens is 1 m m 3 dm m m m 2 4 d m m d m m

cm 4 60 cm Two plano convex lenses of equal focal lengths are arranged as shown DO CD DD The ratio of the combined focal lengths is 2 1 2 3 4 2 1 2 1 1 2 1 3 1 1 1 SAIL on hiect is at a distance u and u from a inge is formed

D C tan Sin r A point object P moves towards a convex mirror with a constant speed V along its optic axis T speed of the image A is always V B may be or V depending on the position of P C decreases as P comes closer to the mirror D increases as P comes closer to the mirror

A thin converging lens L of focal length f and a diverging lens L of focal length f are placed at a distance apart so that their optical axes coincide If a parallel beam of light incident on the first lens L at a small angle a emerges out from the second lens L as a parallel beam mark the correct statements L A Distance between the lenses is f f B Distance between the lenses is fi f C The final emergent beam makes an angle of D The emergent beam will not deviate L 4 a a from the optical axis in clockwise sense f

i A 14 years old student is suffering from a defect of vision He is not able to see clearly the questions written on the chalkboard placed at a distance of 5m from him As such he is prescribed a corrective lens by the doctor a State the nature of the lens that he should use in order to correct the defect of vision b What are the causes of this defect of vision c Write the near point of this student 1 2 1 1 2

A ray of light originates from inside a slab and is incident on its inner surface at an angle 0 as shown 020 72069 9 90 6 206 01 2 TIR OT ve 0 H Glass slab 0 A A A In this experiment the location x of the spot where the ray hits the screen is recorded Which of the following correctly shows the plot of variation of x with the 19 Nov 2017 angle 0 fine why 0 H B B 0 2 BX 0 2 X screen H 0 C C C O H D D 0 D

Example 48 A crown glass prism of angle 5 is to be combined with a flint glass prism in such a way that the mean ray passes undeviated find a the angle of the flint glass prism needed and b the angular dispersion produced by the combination when white light goes through it Refractive indices for red yellow and violet light are 1 514 1 517 and 1 523 respectively for crown glass and 1 613 1 620 and 1 632 for flint glass

A point object O is placed on the principal axis of a convex lens of focal length f 20 cm at a distance of 40 cm to the left of it The diameter of the lens is 10 cm An eye is placed 60 cm to the right of the lens and a distance h below the principal axis The maximum value of h to see the image is assume paraxial approximation to be valid here A B C D 0 2 5 cm 5 cm 10 cm

A Both A and R are true and R is the correct explanation of the assertion B Both A and R are true but R is not the correct explanation of the assertion C A is true but R is false D A is false but R is true 21 22 Assertion A Arterial blood flows with greater pressure Reason R Ventricles are the distributing chambers Assertion Convex mirror is used as a rearview mirror Reason Convex mirror has a positive focal length

The convex side of a lens is silvered as shown in figure A point object starts moving from the focal point of the system on its principal axis away from the lens Then Its image will continuously move towards the system Its image will continuously move away from the lens O Its image will be first real then virtual O Its image will be first virtual then real

Example 40 An isosceles glass prism has one of its equal faces coated with silver A ray is normally incident on the other face and is reflected twice and then emerges perpendicularly Find the angles of prism

A prism of refracting angle 60 makes an angular devia tion of 40 between two rays having a difference of 11 in their angles of incidence Find the refractive index of the material of the prism 1 53

A bi convex lens is formed with two thin plano 2 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 surfaces are of the same radius of curvature R 14 cm For this bi convex lens for an object distance of 40 cm the image distance will be n 1 5 1 280 0 cm 3 21 5 cm n 1 2 R 14 cm 2 40 0 cm 4 13 3 cm fax fuera de n 1 5 1 2 eff R 14 cm 81 effe fra 40 cm ra 1 280 0 cm 3 21 5 cm P n 1 5 1 2 R 14 cm 2 40 0 cm 4 13 3 cm

3 NOR 4 NAND A thin rod of 5 cm length is kept along the axis 43 of a concave mirror of 10 cm focal length such that its image is real and magnified and one end touches the rod Its magnification will be 1 1 2 2 3 3 3 NOR 10 cm 5 cm vas a amafara ga smafia t un 1 1 4 NAND 2 2 gh f ang dat

12 12 A convex lens of focal length f is placed 12 somewhere between an object and a screen The distance between the object and the screen is x If magnitude of the magnification is m the focal length of the lens is given by mx 1 2 m 1 3 mx m 1 m m 1 m Jer a after mat na 3 mx m 1 2 mx m 1 m 1 x m m 1 m ETTET

If the wavelength of light is 4000 then the number of I waves in 1 mm length will be a 25 c 0 25 104 J K CET 2004 GUJCET 2015 b 0 25 d 25 104 rarod waves is greater than that of

The focal length of a concave mirror is 12 cm Where should an object of length 4 cm be placed so that a real image of 1 cm length is formed 1 48 cm 2 3 cm 3 60 cm 4 15 cm

If f is angle substended by two point sources kept at infinity and emitting light of same wavelength at aperture of telescope and is the angular separation between first minima and central maxima of diffraction pattern of the sources the sources are said to be well resolved if A Og 0 B Og 8 C Og 0

IS 4 B refractive index of film should be greater than refractive index of substrate OA Both A and B incorrect OB only A is correct OC only B is correct OD Both A and B are correct

Which of the following are likely reasons that there is not a perfect fit to the trendline observed in the isometric weights spreadsheet The lifter had some fatigue effects Other joint positions shoulder and wrist might change the resistance arm The lifter used slightly different elbow angles with the different weights All of the above are potential reasons

A particular farsighted person s eye can normally focus on an object at 80 cm This person wants to read a book that is held 30 cm from their eye The distance between their corrective lens and their comea the lens of the eye is 2 cm What is the power of their corrective lens O 2 08 m 1 Ob 0 0485 m Oc2 29 m Od 0 0208 m 1 04 85 m 1 Of 4 58 m1 O9 0 0229 m Oh 0 0458 m1 1

This section contains 2 multiple choice MORE THAN ONE answer may be correct 6 Each frosion of Aaquestion has 4 choices 1 2 3 and 4 out of which An object is kept at a distance of 16 cm a thin lens and the image formed is real If the object is kept a a distance of 6 cm from the same lens the image formed is virtual Which of the following statement s is are correct 1 2 If the size of images formed in above two cases are same then the focal length of lens is 11 cm If the size of images formed in above two cases are same then the focal length of lens is 8 cm 34 3 If the size of virtual image is two times of real image then the focal length of lens is 3 28 4 If the size of virtual image is two times of real image then the focal length of lens is 3 cm cm

A prism of refracting angle 4 is made of a material of refractive index 1 652 The angle of minimum deviation of the prism will be O2 608 3 8 O 4 9

For a simple microscope of focal length 12 5 cm the value of magnification for image formed at near point is O 1 2 3

A light ray is of a 90 prism and is totally internally reflected at the glass air interface on other face If the angle of reflection is 45 we conclude that the refractive index u 1 2 1 45 45 Aa 2 2 LC

A convex tens of focal length 50 cm is placed 20 cm in front of a plane mirror Light from very far away source falls on the lens The distance of final image from the mirror is

4 A convex lens of focal length 50 cm is placed 20 cm in front of a plane mirror Light from very far away source falls on the lens The distance of final image from the mirror is Only One Correct Answer A 25 Review cm i

NEET UG 2021 Code 06 24 A convex lens A of focal length 20 cm and concave lens B of focal length 5 cm are kept alor the same axis with a distance d between them a parallel beam of light falling on A leaves B as parallel beam then the distance d in cm will be 1 50 3 25 2 30 4 15

A microscope has an objective of 5 mm focal length and eye piece of 30 mm focal length and the magnification is 250 Then the length of the microscope for normal adjustment will be 1 150 mm 2 50 mm 3 100 mm 4 75 mm

Polarizer and analyzer are crossed at the angle of 6 Find the percentage of the intensity of light passed through that system Select one O 7 7 O 37 5 2 4 O 75

2 A capacitor of capacity 12 micro farad is charged by a battery to a potential difference of 6 volts Then the battery is replaced by another capacitor of capacitance 4 microfarad What will be the charge contained by each capacitor now In the given circuit diagram calculate the charge and potential difference of the 8 uf capacitor 12 v 2 4 F 4 F 8 F 10 A prism of refractive index 1 5 gives an angle of minimum deviation equal to the

A double convex lens made of materials of refractive index 14 is placed inside two liquids of refractive indexes and as shown in figure Where A wide parallel beam of light is incident on lens from left The lens will give rise to Select an answer A Single convergent beam B H C D Two different convergent beam Two different divergent beams Convergent and divergent beam

A converging lens is used to form an image on a screen When the upper half of the lens is covered by an opaque screen Select answers A B C D half the image will disappear complete image will be formed intensity of the image will increase intensity of image will decrease

58 MATCHING TYPE WITH 3 COLUMNS 4 ROWS The following table has 3 columns and 4 rows Based on table there are THREE questions Each question has FOUR options A B C and D ONLY ONE of these four options is correct Column shows four situations with a small ball of mass m connected to an ideal string of length and fastened to a point O whose acceleration if any is shown in the diagram Column 1 lists the minimum value of speed u with respect to point of suspension when the string is vertical in order for the mass to complete the circular motion in vertical plane Column ill lists the maximum tension throughout the circular motion corresponding to minimum speed Column 1 Column 3 Column 2 1 IV O 9 3 l l l 45 5 U u A III P C IV iv R D 2g u 1 3g 6 2g 3 1 ii 5g iv 20g V3 Pick the correct combination from given options A 1 i P C 1 1 Q B II iv R D IV ii P B 11 ii Q D 1 iv S P 6 mg Q 4 3mg Pick the option for combination where maximum tension occurs at 0 0 with vertical A 1 i P C II 1 R B II 1 R D IV i P R 7 mg S 8 mg Pick the correct combination where maximum tension position occurs at greatest possible from vertical

A farsighted person cannot focus distinctly objects closer than 100 cm The lens that will permit him to read from a distance of 50 cm wil have a focal length 1 50 cm 3 100 cm 2 50 cm 4 100 cm

A small object is moving towards a plane mirro with velocity V 10 m s and the plane mirror is moving with velocity V 5 m s as shown The speed of image is Object 1 2 10 m s 3 19 2 m s 45 2 5 5 m s 4 5x10m s