Question 1. An object is placed at a distance of 0.25 m
in front of a plane mirror. The distance between the object and image will be
(a) 0.25 m
(b) 1.0 m
(c) 0.5 m
(d) 0.125 m
Answer/Explanation
Answer: c
Explanation:
(c) Distance between object and image = 0.25 + 0.25 = 0.5 m
Question 2. The angle of incidence for a ray of light having zero reflection angle is
(a) 0
(b) 30°
(c) 45°
(d) 90°
Answer/Explanation
Question 3. For a real object, which of the following can produce a real image?
(a) Plane mirror
(b) Concave mirror
(c) Concave lens
(d) Convex mirror
Answer/Explanation
Answer: b
Explanation:
(b) Only concave mirror can produces a real image for the any position of object between its focus and infinity.
.Question 4. Which of the following mirror is used by a dentist to examine a small cavity?
(a) Convex mirror
(b) Plane mirror
(c) Concave mirror
(d) Combination of convex and concave mirror
Answer/Explanation
Answer: c
Explanation:
(c) Concave mirror forms erect and enlarged image when held close to the cavity.
.Question 5. An object at a distance of 30 cm from a
concave mirror gets its image at the same point. The focal length of the mirror is
(a) – 30 cm
(b) 30 cm
(c) – 15 cm
(d) +15 cm
Answer/Explanation
Answer: c
Explanation:
(c) When object is placed at 2F, the image formed by concave mirror is also at 2F.
So 2F = -30 or F = -15 cm.
.Question 6. An object at a distance of + 15 cm is slowly moved towards the pole of a convex mirror. The image will get
(a) shortened and real
(b) enlarged and real
(c) enlarge and virtual
(d) diminished and virtual
Answer/Explanation
Answer: d
Explanation:
(d) Convex mirror always formed virtual and diminished image.
.Question 7. A concave mirror of radius 30 cm is placed in water. It’s focal length in air and water differ by
(a) 15
(b) 20
(c) 30
(d) 0
Answer/Explanation
Answer: d
Explanation:
(d) The focal length of spherical mirror does not depends on the surrounding medium.
. Question 8. A concave mirror of focal length 20 cm forms an image having twice the size of object. For the virtual position of object, the position of object will be at
(a) 25 cm
(b) 40 cm
(c) 10 cm
(d) At infinity
Answer/Explanation
Answer: c
Explanation:
(c) For virtual image,
.Question 9. The image formed by concave mirror is real, inverted and of the same size as that of the object. 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
Answer/Explanation
Answer: c
Explanation:
(c) When object lies at C of a concave mirror, image is also formed at ‘C’ and having same size real and inverted.
. Question 10. The nature of the image formed by concave mirror when the object is placed between the focus (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
Answer/Explanation
Answer:
Explanation:
(c) When object lies between C and F, the real, inverted and enlarged image is formed beyondC.
.Question 11. The nature of image formed by a convex mirror when the object distance from the mirror is less 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
Answer/Explanation
Answer:
Explanation:
(c) Convex mirror always forms a virtual, erect diminished image irrespective of the position of object in front of it.
.Question 12. If a man’s face is 25 cm in front of concave shaving mirror producing erect image 1.5 times the size of face, focal length of the mirror would be
(a) 75 cm
(b) 25 cm
(c) 15 cm
(d) 60 cm
Answer/Explanation
Answer: a
Explanation:
(a) In concave shaving mirror, virtual erect and large size image, behind the mirror is obtained, using
Hence, focal length of concave mirror is 75 cm.
. Question 13. As light travels from a rarer to a denser medium it will have
(a) increased velocity
(b) decreased velocity
(c) decreased wavelength
(d) both (b) and (c)
Answer/Explanation
Answer:
Explanation:
(d) When light ray travel from rarer to denser medium, its velocity and wavelength both decrease as v = vλ.
.Question 14. The angle of incidence i and refraction r are equal in a transparent slab when the value of i is
(a) 0°
(b) 45°
(c) 90°
(d) depend on the material of the slab
Answer/Explanation
Answer:
Explanation:
(a) When the incident ray falls normally on the glass slab, it will refracted without deviation, i.e. along the normal in the glass slab. So, ∠i = ∠r = 0
.Question 15. The refractive index of transparent medium is greater than one because
(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
Answer/Explanation
Answer: b
Explanation:
. Question 16. The refractive index of water is 1.33. The speed of light in water will be
(a) 1.33 × 108 m/s
(b) 3 × 108 m/s
(c) 2.26 × 108 m/s
(d) 2.66 × 108 m/s
Answer/Explanation
Answer: c
Explanation:
.Question 17. You are given three media A, B and C of refractive index 1.33, 1.65 and 1.46. The medium in which the light will travel fastest is
(a) A
(b) B
(c) C
(d) equal in all three media
Answer/Explanation
Answer: b
Explanation:
So, the light will travel faster in a medium having lower refractive index.
.Question 18. Light from the Sun falling on a convex lens will converge at a point called
(a) centre of curvature
(b) focus
(c) radius of curvature
(d) optical centre
Answer/Explanation
Answer: b
Explanation:
(b) The parallel ray coming from the sun, after refraction through the convex lens converge at its focus.
.Question 19. Large number of thin stripes of black paint are made on the surface of a convex lens of focal 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
(c) a horse of less brightness
(d) a zebra of less brightness
Answer/Explanation
Answer: c
Explanation:
(c) Complete image of the white horse is formed but of less intensity, the light falling on the curved portion will not react at the image position.
Question 20. A divergent lens will produce
(a) always real image
(b) always virtual image
(c) both real and virtual image
(d) none of these
Answer/Explanation
Answer: b
Explanation:
(b) Diverging (concave) lens will always forms a virtual, erect and diminished image.
Question 21. When object moves closer to convex lens, the image formed by it shift
(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
Answer/Explanation
Answer: a
Explanation:
(a) As object moves from infinity towards optical centre of the convex lens image is shifted away from its focal point and towards infinity.
22. When object moves closer to a concave lens the image by it shift
(a) away from the lens on the same side of object
(b) toward the lens
(c) away from the lens on the other side of lens
(d) first towards and then away from the lens
Answer/Explanation
Answer: b
Explanation:
(b) When object infinity, image is formed at the focus of concave lens of object is moved towards lens, the image is also moved from its focus towards lens and its size increase.
23. A magnified real image is formed by a convex lens when the object is at
(a) F
(b) between F and 2F
(c) 2F
(d) only (a) and (b) both
Answer/Explanation
Answer: d
Explanation:
(d) When object is at 2F, real inverted and same size image is formed by convex lens. So, according to question option (a) and (b) both are correct.
24. The distance between the potical centre and point of convergence is called focal length in which of the following cases?
Answer/Explanation
Answer: c
Explanation:
(c) Parallel rays after refiracting meet at the focus of a convex lens.
25. A10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is [NCERT Exemplar Problems]
(a) – 30 cm
(b) – 20 cm
(c) – 40 cm
(d) – 60 cm
Answer/Explanation
Answer: b
Explanation:
(b) Given h0 = +10 mm = + 0.1 cm
h2 = – 5 mm = -0.5 cm
for real image, v = – 30 cm
TO BE CONTINUED WORKSHEET 2 …..