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Chapter 10

Optical Instrument

Encircle the most appropriate answer from the following options  choose which one is correct:

1.         Any transparent medium bounded by one or two spherical surface, is called choose which one is correct:

(a) Lens

(b) Mirror

(c) Prism

(d) None of these

2          what will be the minimum distance from the eye at which an object appears to be distinct is known as the least distance of choose which one is correct:

(a) Focal length

(b) Distinct vision

(c) Focus

(d) All of above

3          A lens which is thicker from middle and thinner from edges called choose which one is correct:

(a) Convex lens

(b) Concave lens

(c) Convex mirror

(d) Concave mirror

4          which lens  is thinner from middle and thicker from edges  choose which one is correct:

(a) Convex lens

(b) Concave mirror

(c) Convex mirror

(d) Concave lens

5          The ratio of the size of image to the size of object is called choose which one is correct:

(a) Magnification

(b) Angular magnification

(c) Classification

(d) None of these

6          The ratio of the angles subtended by the image as seen through the optical device to that angle subtended by the object at the eye is called choose which one is correct:

(a) Linear magnification

(b) Angular magnification

(c) Tabulation

(d) Calculation

7.         A straight line joining the centers of curvature of two surfaces is called choose which one is correct:

(a) Principal axis

(c) Diameter of lens

(d) Principal focus

8          A point where the incident rays of light converge or appears to diverge after passing through the lens is called choose which one is correct:

(a) Aperture

(b) Focus

(c) Optical centre

(d) Pole of lens

9.         When light passes from one medium to another medium, it is bend away from the normal. This phenomenon is called choose which one is correct:

(a) Diffraction

(b) Refraction

(c) Dispersion

(d) Polarization

10.       The distance of near point from the eye is about choose which one is correct:

(a) 25 cm

(b) 25 m

(c) 10 cm

(d) 10 cm

11.       A fixed point inside the lens through which a ray of light does not change its path is called choose which one is correct:

(a) Pole

(b) Principal focus

(c) Optical centre

(d) None of these

12.       The distance between the principal focus and the optical centre of the lens is called choose which one is correct:

(a) Aperture

(b) Focal length

(d) None of these

13        When an object is brought from a far point to the focal point of a convex lens, the size of image  is choose which one is correct:

(a) Unchanged

(b) Decreasing

(c) Increasing

(d) All of above

14`       The apparent size of the object depends upon its actual size and angle subtended by it at the choose which one is correct:

(a) Eye

(b) Face

(c) Mouth

(d) Near point at eye

15        When an object is viewed at a shorter distance, the image on the retina of the eye is choose which one is correct:

(a) Greater

(b) Smaller

(c) Unchanged

(d) None of these

16        The reciprocal of the focal length of a lens is expressed in metres will be known as choose which one is correct:

(a) Power of lens

(b) Focus of lens

(c) Aperture of lens

(d) None of these

17        The unit of power of a lens is choose which one is correct:

(a) Newton

(b) Watt

(c) Dioptre

(d) None of above

18        The power of a convex lens of focal length 50 cm will be choose which one is correct:

(a) 2 dioptre

(b) 5 dioptre

(c) 1.5 dioptre

(d) None of these

19        The focal length of concave lens is choose which one is correct:

(a) Positive

(b) Negative

(c) Positive and negative

(d) None of these

20        The focal length of convex lens is choose which one is correct:

(a) Positive

(b) Negative

(c) Positive and negative

(d) None of these

21        In case of concave lens, the image of the real object is choose which one is correct:

(a) Real, magnified and inverted

(b) Virtual, diminished and erect

(c) Virtual, magnified and erect

(d) None of these

22.       The resolving power of an instrument can be expressed as choose which one is correct:

(a)

(b)

(c)

(d) None of these

23        Raleigh showed that for a light of wavelength 1 through a lens of diameter D, the resolving power is choose which one is correct:

(a)

(b)

(c)

(d) None of these

24.        In case of grating spectrometer, the resolving power R of the grating is defined as choose which one is correct:

(a)

(b)

(c)

(d) None of these

25        The resolving power in the mth order grating equals to choose which one is correct:

(a) R = N x m

(b) R=

(c) R=

(d) R=

26.       If an object is placed in front of convex lens then the image will be choose which one is correct:

(a) Real and erect

(b) Real and inverted

(c) Virtual and erect

(d) Virtual

27        If an object is placed in front of concave lens then the image will be choose which one is correct:

(a) Virtual and erect

(b) Real and inverted

(c) Real and erect

(d) Virtual

28        If an object is placed at 2F from convex lens, the image is located behind the lens choose which one is correct:

(a) Between lens and focus

(b) At 2F

(c) Between F and 2F

(d) At the focus

29        Convex lens forms choose which one is correct:

(a) Real and erect image

(b) Virtual and inverted image

(c) Real and inverted image

(d) None of these

30        If an object is placed slightly more than 2F from a converging lens, the image is located behind the lens choose which one is correct:

(a) At 2F

(b) Between F and 2F

(c) At the focus

(d) None of these

31        Magnification of a lens is positive when the image is choose which one is correct:

(a) Real and inverted

(b) Virtual and inverted

(c) Real and erect

(d) None of these

32.       Magnification of a lens is negative when the image is choose which one is correct:

(a) Real and inverted

(b) Virtual and inverted

(c) Virtual and erect

(d) None of these

33        Magnifying power of an optical instrument is given by the ratio of choose which one is correct:

(a)

(b)

(c)

(d)

34        The magnification of the simple microscope if u and ß are the angles subtended by the object when seen through the lens and when viewed directly is choose which one is correct:

(a)

(b)

(c)

(d)

35.       The magnifying power of a simple microscope is choose which one is correct:

(a) M=1+

(b) M=1+

(c) M =1 + fd

(d) None of these

36        An optical device used for the large magnification of a very minute object is called choose which one is correct:

(a) Simple microscope

(b) Compound microscope

(c) Convex lens

(d) Telescope

37        The convex lens used in compound microscope as objective has focal length choose which one is correct:

(a) Large

(b) Short

(c) Same as eye-piece

(d) None of these

38        If a single convex lens is placed close to the eye then it can be used as choose which one is correct:

(a) Simple microscope

(b) Compound microscope

(c) Spectrometer

(d) Telescope

39        The final image produced by the eye-piece of compound microscope is choose which one is correct:

(a) Real and inverted

(b) Real and erect

(c) Virtual and inverted

(d) Virtual and erect

40        The magnifying power of a compound microscope is choose which one is correct:

(a) M=

(b)  M =

(c) M =

(d) M=

41.       What is the magnifying power of a compound microscope will be choose which one is correct:

(a) Magnification of objective  Magnification of eye-piece

(b) Magnification of objective + Magnification of eye-piece

(c) Magnification of objective x Magnification of eye-piece

(d) Magnification of objective – Magnification of eye-piece

42.       In compound microscope, the focal length of eye-piece is choose which one is correct:

(a) Large

(b) Small

(c) Same as objective

(d) None of these

43        The eye-piece of a compound microscope acts as choose which one is correct:

(a) Converging mirror

(b) Converging lens

(c) Diverging mirror

(d) Diverging lens

44.       If focal length of objective is increased choose which one is correct:

(a) Magnifying power of compound microscope decreased

(b) Magnifying power of astronomical telescope increases

(c) Length of astronomical telescope increases

(d) All of above

45        The resolving power of a compound microscope depends upon choose which one is correct:

(a) The refractive index of the medium in which the object is placed

(b) The angle subtended by the objective lens at the object

(c) The diameter of the objective lens

(d) None of these

46.       It is an optical instrument used to very far off objects is called choose which one is correct:

(a) Telescope

(b) Microscope

(c) Convex lens

(d) Spectrometer

47        A simple astronomical telescope consists of choose which one is correct:

(a) Two convex lens

(b) Two concave lens

(c) One convex and one concave

(d) None of these .

48        The image of a distant object viewed through telescope appears choose which one is correct:

(a) Larger

(b) Brighter

(c) Smaller

(d) Dull

49        The distance between the objective and eye-piece of a telescope in normal adjustment is choose which one is correct:

(a) fo– fc

(b) fo+ fc

(c) fe– fo

(d) None of these

50.       The magnifying power of astronomical telescope is choose which one is correct:

(a)

(b)  = fe,fo

(c)

(d)

51.       The resolving power of an astronomical telescope depends upon choose which one is correct:

(a) The focal length of the objective lens

(b) The least distance of distinct vision of the observer

(c) The focal length of the eye-piece

(d) The diameter of the objective lens

52        The magnifying power of an instrument is expressed in choose which one is correct:

(b) Degrees

(c) No units

(d) None of these

53.       For an astronomical telescope fo + fe = 10 the focal lengths of objective and eye

piece are choose which one is correct:

(a) 50 cm, 5 cm

(b) 210 cm, 25 cm

(c) 100 cm, 5 cm

(d) None of these

54        The final image obtained by astronomical telescope is choose which one is correct:

(a) Erect

(b) Virtual

(c) Magnified

(d) All of them

55        Lenses of focal lengths 100 cm and 5 cm are used as objective and eye-piece of an astronomical telescope, its length for normal adjustment is choose which one is correct:

(a) 95 cm

(b) 105 cm

(c) 20 cm

(d) None of these

56        An optical instrument used to study the properties of light choose which one is correct:

(a) Spectrometer

(b) Simple microscope

(c) Telescope

(d) None of these

57        A grating is placed on the turn table which is capable of rotating about a fixed choose which one is correct:

(a) Vertical axis

(b) Horizontal axis

(c) Both (a) and (b)

(d) None of these

58        The component of the spectrometer which consists of a fixed metallic tube with a convex lens at one end and an adjustable slit is called choose which one is correct:

(a) Telescope

(b) Collimator

(c) Turntable

(d) Grating

59        An instrument which consists of three parts that is collimator, telescope and turn table is called choose which one is correct:

(a) Compound microscope

(b) Spectrometer

(c) Telescope

(d) None of these

60        In spectrometer, the function of collimator is to produce choose which one is correct:

(a) Parallel beam of light

(b) Converging beam of light

(c) Diverging beam of light

(d) None of these

61        The ability of an instrument to reveal the minor details of the object under examination is its choose which one is correct:

(a) Magnification

(b) Resolution

(c) Resolving power

(d) None of these

62. The formula  = 1.22 NA for resolving power was given by choose which one is correct:

(a) Einstein

(b) Newton

(c) Michelson

(d) Raleigh

63.       The scientist who correctly measured the speed of light was choose which one is correct:

(a) Einstein

(b) Michelson

(c) Gallileo

(d) Newton

64.       The scientist who made first attempt to measure the speed of light was choose which one is correct:

(a) Huygen

(b) Young

(c) Einstein

(d) Galileo

65.       Michelson used the equation to find the speed of light is choose which one is correct:

(a)

(b)

(c)

(d)

66.       The speed of light in vacuum or in air is choose which one is correct:

(a) 3 x 1010 m/s

(b) 3 x 107 m/s

(c) 3 x 109m/s

(d) 3 x 108 m/s

67        The speed of light in other materials is always choose which one is correct:

(a) Less than C

(b) Equal to C

(c) Greater than C

(d) None of these

68        In Michelson experiment, the angle subtended by the side of eight sided mirror at the centre is choose which one is correct:

(a)

(b)

(c)

(d)

69        The speed at which light travels within the material depends upon choose which one is correct:

(a) Refractive index

(b) Frequency

(c) Wavelength

(d) Velocity

70        Alexander Bell invented advice known as choose which one is correct:

(a) Photo phone

(b) Telescope

(c) Spectrometer

(d) Microscope

71        Graham Bell was able to transmit a voice message via choose which one is correct:

(a) Telescope

(b) Beam of light

(c) Spectrometer

(d) Simple microscope

72        The detector in photo-phone is made of choose which one is correct:

(a) Selenium

(d) None of these

73.       For incident angles equal or greater than the critical angle, the glass air boundary will act as a choose which one is correct:

(a) Mirror

(b) Concave mirror

(c) Convex mirror

(d) None of these

74        For glass air boundary, the value of critical angle is choose which one is correct:

(a) 41°

(b) 41.5°

(c) 41.8°

(d) 41.2°

75        Optical fibres are of choose which one is correct:

(a) One type

(b) Two types

(c) Three types

(d) None of these

76        A fibre optical communication system consists of choose which one is correct:

(a) Two major components

(b) Three major components

(c) Five major components

(d) Four major components

77        An optical fibre with its protective core may be typically choose which one is correct:

(a) 7 mm

(b) 7.62 cm

(c) 6.0 cm

(d) None of these

78.       Types of optical fibres are choose which one is correct:

(a) Single mode step index

(b) Multimode step index

(d) All of these

79.       Multimode step index fibre is useful for choose which one is correct:

(a) Short distance

(b) Long distance

(c) Neither long nor short

(d) None above

80        Multimode graded index fibre core has diameter of choose which one is correct:

(a) 50 – 2000 um

(b) 50 – 100 um

(c) 50 – 1500 um

(d) 50 – 300 um

81        How many phone calls can be carried by single mode step index fibre choose which one is correct:

(a) 15000

(b) 12000

(c) 16000

(d) 14000

82        The optical fibre is covered for protection by a choose which one is correct:

(a) Plastic jacket

(b) Copper jacket

(c) Glass jacket

(d) Rubber jacket

83        . A layer of lower refractive index over the central core of high refractive index is called choose which one is correct:

(b) Multimode step index fibre

(d) All of the above

84.       Single mode step index fibre has a very thin core of about diameter choose which one is correct:

(a) 2.5 um

(b) 3.5 um

(c) 5.0 um

(d) None of these

85        Multimode step index fibre has a core of relatively larger diameter such as choose which one is correct:

(a) 25 um

(b) 75 um

(c) 100 um

(d) 50 um

86        Light entering glass will not suffer change in choose which one is correct:

(a) Velocity

(b) Direction

(c) Frequency

(d) Wavelength

87        Fibre optics system can be used for choose which one is correct:

(a) Image transmitting

(b) Word processing

(c) Image processing and receiving

(d) All of above

88        Use of outer layer in optical fibres called cladding is mainly to choose which one is correct:

(a) Produce total internal reflection

(b) Scatter the light

(c) Transmit the light

(d) None of these

89        Total internal reflection occurs when the angle of incidence is choose which one is correct:

(a) Equal to critical angle

(b) Greater than critical angle

(c) Less than critical angle

(d) None of these

90        The disadvantages of step index fibre is choose which one is correct:

(a) Quality of the fibre

(b) Size of the cable

(c) Difference in the wavelength of signals

(d) None of these

91        Loss of power in optical fibre results into choose which one is correct:

(a) Accurate information at the receivers

(b) Poor reception of signals

(c) Delay in time for reception of signals

(d) All of these

92        In optical fibres, repeaters are usually laid down after every choose which one is correct:

(a) 1000 km

(b) 10,000 km

(c) 50,000 km

(d) 100 km

93        Television signals are converted into light signals by a device which is one among the following choose which one is correct:

(a) Optical fibre

(b) Transistor

(c) Decoder

(d) Photo diode

94        A convex lens acts as diverging lens when the object is placed choose which one is correct:

(a) At 2F

(b) Within focal length

(c) At forces

(d) Between F and 2F

95        When the object is between F and 2F, the image formed by a convex lens is choose which one is correct:

(a) Real

(b) Virtual

(c) Erect

(d) None of these

96        The ratio of the diameters of two convex lenses is the ratio of their focal lengths choose which one is correct:

(a) Less than

(b) Greater than

(c) Equal to

(d) None of these

97. Conventionally all the distances p, q, f are measured from — of the lens choose which one is correct:

(a) Focus

(b) Optical centre

(c) Edges

(d) None of these

98        A lens of 2 cm focal length is to be used as a magnifying glass. Its magnification is choose which one is correct:

(a) 13.5

(b) 2.5

(c) 0.5

(d) 12.5

99        The working of a compound microscope is based on the principle of choose which one is correct:

(a) Reflection

(b) Refraction

(c) Both (a) and (b)

(d) None

100. Maximum detail of an object can be seen by microscope when the object is illuminated by light of choose which one is correct:

(a) Longer wavelength

(b) Short wavelength

(c) Infrared light

(d) None of these

101. The limit to which a microscope can be used to resolve details of an object depends upon choose which one is correct:

(a) Narrow objective and light of short wavelength

(b) Narrow objective and light of short wavelength

(c) Narrow objective and light of longer wavelength

(d) None of these