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A GIFT FROM SOMNATH SIR

PHYSICS
LIGHT
Class : X

Roll No. : Time -

Date : MM - 267

1. An object is placed at a distance of 0.25 m in front of a plane mirror. The distance between the 1
object and image will be
(a) 0.25 m (b) 1.0 m
(c) 0.5 m (d) 0.125 m

2. The angle of incidence for a ray of light having zero reflection angle is 1
(a) 0 (b) 30°
(c) 45° (d) 90°

3. For a real object, which of the following can produce a real image? 1
(a) Plane mirror (b) Concave mirror
(c) Concave lens (d) Convex mirror

4. Which of the following mirror is used by a dentist to examine a small cavity? 1

(a) Convex mirror
(b) Plane mirror
(c) Concave mirror
(d) Combination of convex and concave mirror

5. An object at a distance of 30 cm from a concave mirror gets its image at the same point. The 1
focal length of the mirror is
(a) – 30 cm (b) 30 cm
(c) – 15 cm (d) +15 cm

6. An object at a distance of +15 cm is slowly moved towards the pole of a convex mirror. The 1
image will get
(a) shortened and real
(b) enlarged and real
(c) enlarge and virtual
(d) diminished and virtual

7. A concave mirror of radius 30 cm is placed in water. It’s focal length in air and water differ by 1
(a) 15 (b) 20
(c) 30 (d) 0

8. A concave mirror of focal length 20 cm forms an image having twice the size of object. For the 1
virtual position of object, the position of object will be at
(a) 25 cm (b) 40 cm
(c) 10 cm (d) At infinity

9. The image formed by concave mirror is real, inverted and of the same size as that of the object. 1
The position of object should be
(a) at the focus
(b) at the centre of curvature
(c) between focus and centre of curvature
(d) beyond centre of curvature

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10. The nature of the image formed by concave mirror when the object is placed between the focus 1
(F) and centre of curvature (C) of the mirror observed by us is
(a) real, inverted and diminished
(b) virtual, erect and smaller in size
(c) real, inverted and enlarged
(d) virtual, upright and enlarged

11. The nature of image formed by a convex mirror when the object distance from the mirror is less 1
than the distance between pole and focal point (F) of the mirror would be
(a) real, inverted and diminished in size
(b) real, inverted and enlarged in size
(c) virtual, upright and diminished in size
(d) virtual, upright and enlarged in size

12. If a man’s face is 25 cm in front of concave shaving mirror producing erect image 1.5 times the 1
size of face, focal length of the mirror would be
(a) 75 cm (b) 25 cm
(c) 15 cm (d) 60 cm

13. As light travels from a rarer to a denser medium it will have 1

(a) increased velocity
(b) decreased velocity
(c) decreased wavelength
(d) both (b) and (c)

14. The angle of incidence i and refraction r are equal in a transparent slab when the value of i is 1
(a) 0°
(b) 45°
(c) 90°
(d) depend on the material of the slab

15. The refractive index of transparent medium is greater than one because 1
(a) Speed of light in vacuum < speed of light in tansparent medium
(b) Speed of light in vacuum > speed of light in tansparent medium
(c) Speed flight in vacuum = speed of light in tansparent medium
(d) Frequency of light wave changes when it moves from rarer to denser medium

16. The refractive index of water is 1.33. The speed of light in water will be 1
(a) 1.33 × 108 m/s (b) 3 × 108 m/s
(c) 2.26 × 108 m/s (d) 2.66 × 108 m/s

17. You are given three media A, B and C of refractive index 1.33, 1.65 and 1.46. The medium in 1
which the light will travel fastest is
(a) A
(b) B
(c) C
(d) equal in all three media

18. Light from the Sun falling on a convex lens will converge at a point called 1
(a) centre of curvature
(b) focus
(c) radius of curvature
(d) optical centre

19. Large number of thin stripes of black paint are made on the surface of a convex lens of focal 1
length 20 cm to catch the image of a white horse. The image will be
(a) a zebra of black stripes
(b) a horse of black stripes

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(c) a horse of less brightness
(d) a zebra of less brightness

20. A divergent lens will produce 1

(a) always real image
(b) always virtual image
(c) both real and virtual image
(d) none of these

21. When object moves closer to convex lens, the image formed by it shift 1
(a) away from the lens
(b) towards the lens
(c) first towards and then away from the lens
(d) first away and then towards the lens

22. A magnified real image is formed by a convex lens when the object is at 1
(a) F
(b) between F and 2F
(c) 2F
(d) only (a) and (b) both

23. The distance between the potical centre and point of convergence is called focal length in which 1
of the following cases?

24. A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the 1
awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is
(a) – 30 cm (b) – 20 cm
(c) – 40 cm (d) – 60 cm

25. Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the 1
medium B relative to medium A is

26. A light ray enters from medium A to medium B as shown in figure. The refractive index of 1
medium B relative to A will be

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(a) greater than unity

(b) less than unity
(c) equal to unity
(d) zero

27. Beams of light are incident through the holes A and B and emerge out of box through the holes C 1
and D respectively as shown in the figure. Which of the following could be inside the box?

(a) A rectangular glass slab

(b) A convex lens
(c) A concave lens
(d) A prism

28. A beam of light is incident through the holes on side A and emerges out of the hole on the other 1
face of the box as shown in the figure. Which of the following could be inside the box?
(a) Concave lens
(b) Rectangular glass slab
(c) Prism
(d) Convex lens

29. Which of the following statements is/are true? 1

(a) A convex lens has 4 dioptre power having a focal length 0.25 m
(b) A convex lens has –4 dioptre power having a focal length 0.25 m
(c) A concave lens has 4 dioptre power having a focal length 0.25 m
(d) A concave lens has – 4 dioptre having a focal 0.25 m

30. Magnification produced by a rear view mirror fitted in vehicles 1

(a) is less than one
(b) is more than one
(c) is equal to one
(d) can be more than or less than one depending upon the position of the object in front of it.

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31. A full length image of a distant tall building can definitely be seen by using 1
(a) a concave mirror
(b) a convex mirror
(c) a plane mirror
(d) both concave as well as plane mirror

32. In torches, search lights and headlights of vehicles the bulb is placed 1
(a) between the pole and the focus of the reflector
(b) very near to the focus of the reflector
(c) between the focus and centre of curvature of the reflector
(d) at the centre of curvature of the

33. The laws of reflection hold good for 1

(a) plane mirror only
(b) concave mirror only
(c) convex mirror only
(d) all mirrors irrespective of their shape

34. The path of a ray of light coming from air passing through a rectangular glass slab traced by four 1
students are shown as A, B, C and D in figure. Which one of them is correct?

(a) A (b) B
(c) C (d) D

35. In which of the following, the image of an object placed at infinity will be highly diminished and 1
point sized?
(a) Concave mirror only
(b) Convex mirror only
(c) Convex lens only
(d) Concave mirror, convex mirror, concave lens and convex lens.

36. The questions given below consist of an assertion and the reason. Use the following key to 1
choose the appropriate answer.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the
Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the
Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Assertion: Incident light is reflected in only one direction from a smooth surface.
Reason: Since the angle of incidence and the angle of reflection are same, a beam of parallel rays
of light falling on a smooth surface is reflected as a beam of parallel light rays in one direction only.

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37. The questions given below consist of an assertion and the reason. Use the following key to 1
choose the appropriate answer.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the
Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the
Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Assertion: The word AMBULANCE on the hospital vans is written in the form of its mirror as
AMBULANCE .
Reason: The image formed in a plane mirror is same size of the oblect.

38. The questions given below consist of an assertion and the reason. Use the following key to 1
choose the appropriate answer.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the
Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the
Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Assertion: Cannot see the distant object clearly.

Reason: The far point of an eye suffering from myopia is less than infinity.

39. The questions given below consist of an assertion and the reason. Use the following key to 1
choose the appropriate answer.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the
Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the
Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Assertion: Pupil is black in colour.

Reason: Pupil is black in colour as no light is reflected in it.

40. The questions given below consist of an assertion and the reason. Use the following key to 1
choose the appropriate answer.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the
Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the
Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Assertion: The rainbow is a man made spectrum of sunlight in the sky.

Reason: The rainbow is formed in the sky when the sun is shining and it is raining at the same time.

41. ________________ mirror is used as a security mirror in shops and on roads at sharp bends 1
and concealed entrances.

42. The refractive index of a transparent medium is the ratio of the speed of light in _____________ 1
to that in the _____________.

43. If the magnification has a minus sign, then the image is _____________ and _____________. 1

44. The focal length of a lens is the distance between _____________ and _____________ of the 1
lens.

45. The focal length of a concave lens is considered to be _____________. 1

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46. In order to calculate the power of a lens, we need its focal length in _____________. 1

47. Angle of refraction cannot exceed 90°. [True/False] 1

48. 1
When incident angle i satisfies n = the refracted light will pass along the surface.
[True/False]

49. A person standing in front of a mirror finds his image larger than himself. This shows that mirror 1
is convex in nature. [True/False]

50. Lateral displacement increases with the thickness of the given slab. [True/False] 1

51. Lateral displacement is directly proportional to thickness of the glass slab. [True/False] 1

52. Nature of image formed by mirror gives an ideal about nature of mirror. [True/False] 1

53. A convex lens (ng = 3/2) when placed in water (nw = 4/3) has increased focal length [True/False] 1

54. A convex and a concave lens of equal focal length behaves as a regular glass slab receiving 1
light normally. [True/False]

55. Concave lens and convex mirror diverge the rays which fall parallel to the principal axis. 1
[True/False]

56. The power of a concave lens is positive. 1

[True/False]

57. Match Column I with Column II. 1

Column I Column II
(i) Ray through centre of (A) Reflected parallel to
curvature principal axis
(ii) Ray through focus (B) Converge at focus
(iii) Rays from infinite
(C) Emerge through focus
distance
(iv) Refracted rays to infinity (D) Retracing in mirrors

58. If angle of incidence is 0°, what is the angle of reflection? 1

59. The angle between incident ray and reflected ray is 60°. What is the angle of incidence? 1

60. What is the magnification of the images formed by plane mirrors and why? 1

61. Explain why a ray of light passing through the centre of curvature of a concave mirror, gets 1
reflected along the same path.

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62. Redraw the diagram given below in your answer book and show the direction of the light ray 1
after reflection from the mirror.

63. A concave mirror forms a sharp image of a distant tree. What name is given to the distance 1
between the concave mirror and screen on which sharp image is formed?

64. In what condition, the image formed by a concave mirror is virtual? 1

65. Specified the size of image formed by a concave mirror when m > 1. 1

66. Name the mirror that can be used to check theft in shops. 1

67. What is the position of the object placed on the side of reflecting surface of a concave mirror of 1
focal length 15 cm if the image is formed at the distance of 30 cm from the mirror?

68. Which mirror, concave or convex always converges the light rays? 1

69. When light undergoes refraction at the surface of two media, what happens to the speed of light? 1

70. Can absolute refractive index of any material be less than one? 1

71. Why does a ray of light bend when it travels from one medium into another? 1

72. If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray. 1

73. Does the value of speed of light change with medium? 1

74. The following table gives the values of refractive indices of a few media. 1

S.No. Medium Refractive Index

1. Water 1.33
2. Crown glass 1.52
3. Rock salt 1.54
4. Ruby 1.71
5. Diamond 2.42

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Use this table to give an example of a medium pair so that light speeds up when it goes from one
of these media to another.

75. The speed of light in a transparent medium is 0.6 times that of its speed in vacuum. What is the 1
refractive index of the medium?

76. Redraw the given diagram and show the path of the refracted ray. 1

77. Redraw the diagram given below in your answer book and show the direction of the light ray 1
after refraction from the lens.

78. An object is held at the principal focus of a concave lens of focal length f. Where the image will 1
form?

79. A girl was playing with a thin beam of light from her laser torch by directing it from different 1
directions on a convex lens held vertically. She was surprised to see that in a particular direction the
beam of light continues to move along the same direction after passing through the lens. State the
reason for this observation.

80. Is it possible to form a real image using a real object with a concave lens? 1

81. Draw the following diagram in which a ray of light is incident on a concave/convex mirror on your 3
answer sheet. Show the path of this ray, after reflection, in each case.

82. The image of an object formed by a mirror is real, inverted and is of magnification –1. If the 3
image is at a distance of 40 cm from the mirror, where is the object placed? Where would the image
be if the object is moved 20 cm towards the mirror? State reason and also draw ray diagram for the
new position of the object to justify your answer.

83. A spherical mirror produces an image of magnification –1 on a screen placed at a distance of 50 3

cm from the mirror.
(a) Write the type of mirror.
(b) Find the distance of the image from the object.
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(c) What is the focal length of the mirror?
(d) Draw the ray diagram to show the image formation in this case.

84. A student wants to project the image of a candle flame on a screen 80 cm in front of a mirror by 3
keeping the candle flame at a distance of 20 cm from its pole.
(i) Which type of mirror should the student use?
(ii) Find the magnification of the image produced.
(iii) Find the distance between the object and its image.
(iv) Draw a ray diagram to show the image formation in this case and mark the distance between
the object and its image.

85. A student wants to obtain an erect image of an object using a concave mirror of 12 cm focal 3
length. What should be the range of distance of the object from the mirror? State the nature and
size of the image he is likely to observe. Draw a ray diagram to justify your answer.

86. For the given data showing the focal lengths of three concave mirrors A, B and C, and the 3
respective distances of different objects from these mirrors.

Object distance Focal length

S.No.
(cm) (cm)

A 45 20

B 30 15

C 20 30

Answer the following questions:

(i) In the given position of object from the mirrors, which mirror will form a diminished image of the
object. Draw a ray diagram for image formation by this mirror.
(ii) Which mirror can be conveniently used as a make-up mirror? Draw a ray diagram to illustrate
this function.

87. Name the type of mirror used (i) by dentists and (ii) shaving mirrors. Give two reasons why such 3
mirrors are used in each case.

88. Draw a ray diagram to show the path of the reflected ray in each of the following cases. A ray of 3
light incident on a convex mirror.
(a) strikes at its pole making an angle from the principal axis.
(b) is directed towards its principal focus.
(c) is parallel to its principal axis.

89. If the image formed by mirror for all positions of the object placed in front of it is always virtual 3
and diminished, state the type of the mirror. Draw a ray diagram in support of your answer. Where
are such mirrors commonly used and why?

90. A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the 3
location of the image and magnification. Describe what happens as the needle is moved farther
from the mirror?

91. (a) “The refractive index of diamond is 2.42”. What is the meaning of this statement? 3
(b) Name a liquid whose mass density is less than that of water but it is optically denser than water.

92. What is understood by lateral displacement of light? Illustrate it with the help of a diagram. List 3
any two factors on which the lateral displacement of a particular substance depends.

93. (a) Draw a ray diagram to show the path of a light ray passes from one medium to another if the 3
two media are optically exactly the same.

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(b) Absolute refractive indices of medium ‘A’ and medium ‘B’ are ‘na’ and ‘nb’ respectively. What is
the refractive index of medium ‘B’ with respect to medium ‘A’.
(c) How does the velocity of light vary with change in the optical density of the media?

94. A coin is kept at the bottom of an empty bucket. A student standing near to it cannot see the coin. 3
Another student pours some water into the bucket without disturbing the coin. Now, the first student
is able to see the coin from the same position. Explain how it become possible to see the coin now?
Draw a ray diagram to illustrate it.

95. (a) Differentiate between reflection and refraction. 3

(b) A lemon kept in water in a glass tumbler appears to be bigger than its actual size, when viewed
from the sides. Explain why it so appears.

96. A ray of light is incident on the interface separating diamond and water. Given that refractive 3
indices of diamond and water with respect to air are 2.42 and 1.33 respectively, complete the
diagram by showing a refracted ray and mark the angles of incidence and refraction.

97. State the laws of refraction of light. If the speed of light in vacuum is 3 × 108 m/s, find the 3
absolute refractive index of a medium in which light travels with a speed of 1.4 × 108 m/s.

98. An object of height 6 cm is placed perpendicular to the principal axis of a concave lens of focal 3
length 5 cm. Use lens formula to determine the position, size and nature of the image if the
distance of the object from the lens is 10 cm.

99. If the image formed by a lens for all positions of the object placed in front of it is always virtual, 3
erect and diminished, state the type of the lens. Draw a ray diagram in support of your answer. If
the numerical value of focal length of such a lens is 20 cm, find its power in new cartesian sign
conventions.

100.An object of height 5 cm is placed perpendicular to the principal axis of a concave lens of focal 3
length 10 cm. If the distance of the object from the optical centre of the lens is 20 cm, determine the
position, nature and size of the image.

101.Draw a ray diagram to show the path of the refracted ray in each of the following cases: A ray of 3
light incident on a concave lens is
(i) passing through its optical centre.
(ii) parallel to its principal axis.
(iii) directed towards its principal focus.

102.The image of a candle flame placed at a distance of 30 cm from a spherical lens is formed on a 3
screen placed on the other side of the lens at a distance of 60 cm from the optical centre of the
lens. Identify the type of lens and calculate its focal length. If the height of the flame is 3 cm, find
the height of its image.

103.A 6 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 15 3
cm. The distance of the object from the lens is 10 cm. Find the position, size and nature of the
image formed, using the lens formula.

104.A convex lens has a focal length of 10 cm. At what distance from the lens should the object be 3
placed so that it forms a real and inverted image 20 cm away from the lens? What would be the
size of the image formed if the object is 2 cm high? With the help of a ray diagram show the
formation of the image by the lens in this case.

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105.An object placed on a metre scale at 8 cm mark was focussed on a white screen placed at 92 3
cm mark, using a converging lens placed on the scale at 50 cm mark.
(i) Find the focal length of converging lens.
(ii) Find the position of the image formed if the object is shifted towards the lens at a position of
29.0 cm.
(iii) State the nature of the image formed if the object is further shifted towards the lens.

106.An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex 3
lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on
the screen. What is the focal length of the convex lens and size of the image formed on the screen
? Draw a ray diagram to show the formation of the image in this position of the object with respect
to the lens.

107.(a) Two lenses have powers of (i) + 2D and (ii) – 4D. What is the nature and focal length of each 3
lens?
(b) An object is kept at a distance of 100 cm from each of the above lenses. Calculate the (i) image
distance and (ii) magnification in each of the two cases.

108.An object is kept at a distance of 18 cm, 20 cm, 22 cm and 30 cm respectively from a lens of 3
power +5D.
(i) In which case or cases would you get a magnified image?
(ii) Which of the magnified image can be got on a screen?

109.(a) What is the focal length of the lens used in sunglasses? 3

(b) The following figures show the path of light rays through three lenses marked L1, L2 and L3 and
their focal points F1, F2 and F3 respectively. Identify the nature of lenses.

110.(a) Define the following terms in the context of spherical mirrors: 5

(i) Pole (ii) Centre of curvature (iii) Principal axis (iv) Principal focus
(b) Draw ray diagrams to show the principal focus of a (i) concave mirror (ii) convex mirror
(c) Consider the following diagram in which M is a mirror and P is an object and Q is its magnified

image formed by the mirror.

State the type of the mirror M and one characteristic property of the image Q.

111.(a) To construct a ray diagram, we use two light rays which are so chosen that it is easy to know 5
their directions after reflection from the mirror. List these two rays and state the path of these rays
after reflection. Use these rays to locate the image of an object placed between centre of curvature
and focus of a concave mirror.
(b) Draw a ray diagram to show the formation of image of an object placed between the pole and
principal focus of a concave mirror. How will the nature and size of the image formed change, if the
mirror is replaced by converging lens of same focal length?

112.List the new Cartesian sign convention for reflection of light by spherical mirrors. Draw a 5
diagram and apply these conventions for calculating the focal length and nature of a spherical
mirror which forms a 1/3 times magnified virtual image of an object placed 18 cm in front of it.

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113.It is desired to obtain an erect image of an object, using concave mirror of focal length of 12 cm. 5
(i) What should be the range of distance of an object placed in front of the mirror?
(ii) Will the image be smaller or larger than the object? Draw ray diagram to show the formation of
image in this case.
(iii) Where will the image of this object be, if it is placed 24 cm in front of the mirror? Draw ray
diagram for this situation also to justify your answer.
Show the positions of pole, principal focus and the centre of curvature in the above ray diagrams.

114.Suppose you have three concave mirrors A, B and C of focal lengths 10 cm, 15 cm and 20 cm. 5
For each concave mirror you perform the experiment of image formation for three values of object
distances of 10 cm, 20 cm and 30 cm. Giving reason answer the following:
(a) For the three object distances, identify the mirror/mirrors which will form an image of
magnification –1.
(b) Out of the three mirrors identify the mirror which would be preferred to be used for shaving
purposes/make-up.
(c) For the mirror B draw ray diagram for image formation for object distances 10 cm and 20 cm.

115.A student has focussed the image of a candle flame on a white screen using a concave mirror. 5
The situation is as given below:
Length of the flame = 1.5 cm
Focal length of the mirror = 12 cm
Distance of flame from the mirror = 18 cm
If the flame is perpendicular to the principal axis of the mirror, then calculate the following:
(a) Distance of the image from the mirror
(b) Length of the image.
If the distance between the mirror and the flame is reduced to 10 cm, then what would be observed
on the screen? Draw ray diagram to justify your answer for this situation.

116.(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium 5
and write an expression to relate it with the speed of light in vacuum.
(b) The absolute refractive indices of two media ‘A’ and ‘B’ are 2.0 and 1.5 respectively. If the speed
of light in medium ‘B’ is 2 × 108 m/s, calculate the speed of light in:
(i) vaccum, (ii) medium ‘A’.

117.(a) Explain the following terms related to spherical lenses: 5

(i) Optical centre (ii) Centres of curvature
(iii) Principal axis (iv) Aperture
(v) Principal focus (vi) Focal length
(b) A converging lens has focal length of 12 cm. Calculate at what distance should the object be
placed from the lens so that it forms an image at 48 cm on the other side of the lens.

118.List the sign conventions that are followed in case of refraction of light through spherical lenses. 5
Draw a diagram and apply these conventions in determining the nature and focal length of a
spherical lens which forms three times magnified real image of an object placed 16 cm from the
lens.

119.(a) Draw a ray diagram to show the formation of image by a convex lens when an object is 5
placed in front of the lens between its optical centre and principal focus.
(b) In the above ray diagram mark the object-distance (u) and the image-distance (v) with their
proper signs (+ve or –ve as per the new Cartesian sign convention) and state how these distances
are related to the focal length (f) of the convex lens in this case.
(c) Find power of a convex lens which forms a real, and inverted image of magnification –1 of an
object placed at a distance of 20 cm from its optical centre.

120.One-half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens 5
produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray
diagram to justify your answer.
A 4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20
cm. The distance of the object from the lens is 15 cm. Find the nature, position and size of the
image.

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5/26/24, 2:49 PM Test Generator
121.“A convex lens can form a magnified erect as well as magnified inverted image of an object 5
placed in front of it”. Draw ray diagram to justify this statement stating the position of the object with
respect to the lens in each case.
An object of height 4 cm is placed at a distance of 20 cm from a concave lens of focal length 10 cm.
Use lens formula to determine the position of the image formed.

122.A student wants to project the image of a candle flame on the walls of school laboratory by 5
using a lens.
(a) Which type of lens should he use and why?
(b) At what distance in terms of focal length ‘f ’ of the lens should he place the candle flame so as to
get (i) a magnified, and (ii) a diminished image respectively on the wall?
(c) Draw ray diagram to show the formation of the image in each case.

123.(a) Define optical centre of a spherical lens. 5

(b) A divergent lens has a focal length of 20 cm. At what distance should an object of height 4 cm
from the optical centre of the lens be placed so that its image is formed 10 cm away from the lens.
Find the size of the image also.
(c) Draw a ray diagram to show the formation of image in above situation.

124.At what distance from a concave lens of focal length 20 cm, a 6 cm tall object be placed so as 5
to
obtain its image at 15 cm from the lens? Also calculate the size of the image formed. Draw a ray
diagram to justify your answer for the above situation and label it.

125.(a) If the image formed by a lens is diminished in size and erect, for all positions of the object, 5
what type of lens is it?
(b) Name the point on the lens through which a ray of light passes undeviated.
(c) An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm.
The distance of the object from the lens is 30 cm. Find (i) the position (ii) the magnification and (iii)
the nature of the image formed.

126.(a) Under what condition will a glass lens placed in a transparent liquid become invisible? 5
(b) Describe and illustrate with a diagram, how we should arrange two converging lenses so that a
parallel beam of light entering one lens emerges as a parallel beam after passing through the
second lens.
(c) An object is placed at a distance of 3 cm from a concave lens of focal length 12 cm. Find the (i)
position and (ii) nature of the image formed.

127.(a) Why is the magnification produced by a concave lens always less than 1? 5
(b) You are provided with two lenses of focal lengths 10 cm and 20 cm. Which of the two lenses
would you suggest to obtain greater convergence of refracted light? Justify your choice.
(c) An image 2/3rd the size of object is formed by a convex lens at a distance of 12 cm from it. Find
the focal length of the lens.

128.(a) A concave lens is called a diverging lens. Explain this property with the help of diagram. 5
(b) For a concave mirror draw a ray diagram to show the reflected ray when the ray of light incident
obliquely on the pole of mirror.
(c) What is the difference between virtual images produced by concave, plane and convex mirrors?

129.What is meant by power of a lens? Define its S.I. unit. 5

You have two lenses A and B of focal lengths +10 cm and –10 cm respectively. State the nature and
power of each lens.
Which of the two lenses will form a virtual and magnified image of an object placed 8 cm from the
lens? Draw a ray diagram to justify your answer.

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