CLICK HERE FOR LIGHT WORKSHEET 1
26. Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is [NCERT Exemplar Problems]
Answer/Explanation
Answer: a
Explanation:
(a) Here, ∠i = 60°, ∠r = 45°
Using Snell’s law of refraction, refractive index of medium B with respect to medium A.
27. A light ray enters from medium A to medium B as shown in figure. The refractive index of medium B relative to A will be [NCERT Exemplar Problems]
(a) greater than unity
(b) less than unity
(c) equal to unity
(d) zero
Answer/Explanation
Answer: b
Explanation:
(b) In medium B, light ray bends away from the normal. It indicates that medium B is optically rarer than medium A. Hence speed of light in medium B is more than that in medium A.
Now, refractive index
28. Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the figure. Which of the following could be inside the box? [NCERT Exemplar Problems]
(a) A rectangular glass slab
(b) A convex lens .
(c) A concave lens
(d) A prism
Answer/Explanation
Answer: a
Explanation:
(a) Figure shows that emergent ray are parallel to the incedent ray and shifted side ward slightly. This can be done by the rectangular glass slab only.
29. A beam of light is incident through the holes on side A and emerges out of the hole on the other face of the box as shown in the figure. Which of the following could be inside the box? [NCERT Exemplar Problems]
(a) Concave lens
(b) Rectangular glass slab
(c) Prism
(d) Convex lens
Answer/Explanation
Answer: d
Explanation:
(d) From figure, it is clear that parallel rays converge at a point and emerges from face B. So convex lens would be possible inside the box.
30. Which of the following statements is/are true? [NCERT Exemplar Problems]
(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
Answer/Explanation
Answer: a
Explanation:
(a) Positive sign with power and focal length indicates that the given lens is convex.
Also f = 1P=14 = 0.25m
31. Magnification produced by a rear view mirror fitted in vehicles [NCERT Exemplar Problems]
(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.
Answer/Explanation
Answer: a
Explanation:
(a) Convex mirror is used as rear view mirror and alway forms virtual, erect and diminished inage. So magnification produced by a rear view mirror is less than one.
32. A full length image of a distant tall building can definitely be seen by using [NCERT Exemplar Problems]
(a) a concave mirror
(b) a convex mirror
(c) a plane mirror
(d) both concave as well as plane mirror
Answer/Explanation
Answer: b
Explanation:
(b) Convex mirror has a wide field of view as it forms virtual, erect and diminished image. Hence, fall length of image of distance tall building can definitely be seen by using it.
33. In torches, search lights and headlights of vehicles the bulb is placed [NCERT Exemplar Problems]
(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 reflector
Answer/Explanation
Answer: b
Explanation:
(b) When source of light is placed verg near to the focus of the reflector which are concave in shape, the reflected light becomes parallel to the principal axis.
34. The laws of reflection hold good for [NCERT Exemplar Problems]
(a) plane mirror only
(b) concave mirror only
(c) convex mirror only
(d) all mirrors irrespective of their shape
Answer/Explanation
Answer: d
Explanation:
(d) The laws of reflection hold good for light reflected from any smooth surface irrespective of their shapes.
35. The path of a ray of light coming from air passing through a rectangular glass slab traced by four students are shown as A, B, C and D in figure. Which one of them is correct? [NCERT Exemplar Problems]
(a) A
(b) B
(c) C
(d) D
Answer/Explanation
Answer: b
Explanation:
(b) When a light ray is incident oblikely on one face of rectangular glass slab, the emergent ray will be parallel to the incident ray and shifted sideward slightly.
36. In which of the following, the image of an object placed at infinity will be highly diminished and point sized? [NCERT Exemplar Problems]
(a) Concave mirror only
(b) Convex mirror only
(c) Convex lens only
(d) Concave mirror, convex mirror, concave lens and convex lens.
Answer/Explanation
Answer: d
Explanation:
(d) The incident ray coming from the object placed at infinity will be parallel to the principal axis. When the parallel beam of light incident on a mirror or lens, irrespective of their nature, after reflection/refraction, will pass or appear to pass through their principal focus. Hence highly diminished and point size image will be formed at their focus.
37. When light falls on a smooth polished surface, most of it
(a) is reflected in the same direction
(b) is reflected in different directions
(c) is scattered
(d) is refracted into the second medium
Answer
Answer: a
38. Image formed by reflection from a plane mirror is
(a) real and inverted
(b) virtual and erect
(c) real and erect
(d) virtual and inverted
Answer
Answer: b
39. If an incident ray passes through the focus, the reflected ray will
(a) pass through the pole
(b) be parallel to the principal axis
(c) retrace its path
(d) pass through the centre of curvature
Answer
Answer: b
40. Magnifying power of a concave lens is
(a) always > 1
(b) always < 1
(c) always = 1
(d) can have any value
Answer
Answer: b
41. The image formed by a convex lens can be
(a) virtual and magnified
(b) virtual and diminished
(c) virtual and of same size
(d) virtual image is not formed
Answer
Answer: a
42. A point object is placed at a distance of 20 cm from a convex mirror of focal length 20 cm. The image will form at:
(a) at infinity
(b) at focus
(c) at the pole
(d) behind the mirror
Answer
Answer: d
43. Focal length of a concave mirror is
(a) negative
(b) positive
(c) depends on the position of object
(d) depends on the position of image
Answer
Answer: a
44. If the power of a lens is – 2 D, what is its focal length?
(a) +50 cm
(b) -100 cm
(c) -50 cm
(d) +100 cm
Answer
Answer: c
45. A spherical mirror and a spherical lens each have a focal length of -10 cm. The mirror and the lens are likely to be
(a) both concave
(b) both convex
(c) the mirror is concave and the lens is convex
(d) the mirror is convex and the lens is concave
Answer
Answer: a
46. If the magnification produced by a lens has a negative value, the image will be
(a) virtual and inverted
(b) virtual and erect
(c) real and erect
(d) real and inverted
Answer
Answer: b
47. When the object is placed between f and 2f of a convex lens, the image formed is
(a) at f
(b) at 2f
(c) beyond 2f
(d) between O and f
Answer
Answer: c
48. Which mirroji can produce a virtual, erect and magnified ifhage of an object?
(a) Concave mirror
(b) Convex mirror
(c) Plane mirror
(d) Both concave and convex mirrors
Answer
Answer: a
49. If the image is formed in front of the mirror, then the image distance will be
(a) positive or negative depending on the size of the object
(b) neither positive nor negative
(c) positive
(d) negative
Answer
Answer: d
50. A ray of light is travelling from a rarer medium to a denser medium. While entering the denser medium at the point of incidence, it
(a) goes straight into the second medium
(b) bends towards the normal
(c) bends away from the normal
(d) does not enter at all
Answer
Answer: b
51. A student does the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. He can get a correct measure of the angle of incidence and the angle of emergence by following the labelling indicated in figure:
(a) I
(b) II
(c) III
(d) IV
Answer
Answer: d
Direction (Q52 to Q56): The questions given below consist of an assertion and the reason. Use the following key to 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.
52. 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.
Answer/Explanation
Answer: a
Explanation:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
53. Assertion: The word AMBULANCE on the hospital vans is written in the form of its mirror as
Reason: The image formed in a plane mirror is same size of the oblect.
Answer/Explanation
Answer: b
Explanation:
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
54. Assertion: Cannot see the distant object clearly.
Reason: The far point of an eye suffering j, from myopia is less than infinity.
Answer/Explanation
Answer: b
Explanation:
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
55. Assertion: Pupil is black in colour.
Reason: Pupil is black in colour as no light is reflected in it.
Answer/Explanation
Answer: a
Explanation:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
56. 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.
Answer/Explanation
Answer: a
Explanation:
(a) The statement of the Assertion is false but the Reason is true.
57. ____________ mirror is used as a security mirror in shops and on roads at sharp bends and concealed entrances.
Answer/Explanation
Answer:
Explanation: Convex
58. The refractive index of a transparent medium is the ratio of the speed of light in ____________ to that in the ____________ .
Answer/Explanation
Answer:
Explanation: vacuum, medium
59. If the magnification has a minus sign, then the image is ____________ and ____________ .
Answer/Explanation
Answer:
Explanation: real, inverted
60. The focal length of a lens is the distance between ____________ and ____________ of the lens.
Answer/Explanation
Answer:
Explanation: optical centre, principal focus
TO BE CONTINUED WORKSHEET 3…….