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Quiz 5
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Q.1
A person standing in front of mirror finds his image thinner but with normal height. this implies that the mirror is
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a) convex and spherical
0%
b) concave and spherical
0%
c)Convex and cylindrical with axis vertical
0%
d)Convex and cylindrical with axis horizontal
Explanation
Answer:(c)
Q.2
A point object is placed mid-way between two plane mirror distance 'a' apart. the plane mirror forms an infinite number of images due to multiple reflection. The distance between the nth order image formed in the two mirrors is
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a) na
0%
b) 2na
0%
c) na/2
0%
d) n2a
Explanation
Answer: (b)
Q.3
A convergent beam of light converges to a point 20cm behind the convex mirror on the principle axis. An inverted image of the same size is coincident with the virtual object. Then the focal length of the convex mirror is
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a)20 cm
0%
b) 10 cm
0%
c)40 cm
0%
d)30 cm
Explanation
Answer: (b)
Q.4
Rays of light strikes a horizontal plane mirror at an angle of 45°. A second plane mirror is arranged at an angle θ with it. If the ray after reflection from the second mirror runs horizontally i.e. parallel to the first mirror then θ is
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a) 45°
0%
b) 60°
0%
c)67°30'
0%
d)135°
Explanation
Answer: (c)
Q.5
A diminished virtual image can be obtained only in
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a) A plane mirror
0%
b) A concave spherical mirror
0%
c)A convex spherical mirror
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d)A concave spherical mirror
Explanation
Answer:(c)
Q.6
A convergent beam of light is incident on a convex mirror of radius of curvature 0.6m as shown in figure. The image formed by the convex mirror is
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a) Virtual and 15 cm behind the mirror
0%
b) Real and 15 cm in front of the mirror
0%
c) Virtual and 7.5 cm behind the mirror
0%
d) Real and 7.5 cm in front of the mirror
Explanation
Answer: (b)
Q.7
A ray of light is incident on a plane mirror at an angle of incidence of 30°. The deviation produced by the mirror is :
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a)30°
0%
b) 90°
0%
c)120 °
0%
d)60 °
Explanation
Answer: (c)
Q.8
A small piece of wire bent into an L shape with upright and horizontal portions of equal lengths, is placed with the horizontal portion along the axis of the concave mirror whose radius of curvature is 10 cm. If the bend is 20 cm from the pole of the mirror, then the ratio of the lengths of the image of the upright and horizontal portions of the wire is
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a) 1:2
0%
b) 3:1
0%
c)1:3
0%
d)2 : 1
Explanation
Answer: (b)
Q.9
The magnification m , the image position v and focal length f are related to one another by the relation
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
Answer:(a)
Q.10
The relation between magnification m, the objective position u and focal length f of the mirror is
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
Answer: (b)
Q.11
A concave mirror forms an errect image of twice its size, object distance from the mirror is
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a)f/2
0%
b) f/4
0%
c) 3f/2
0%
d)2f
Explanation
Answer: (a)
Q.12
A convex mirror of focal length f produces an image (1/n)th of the size of the object. The distance of the object from the mirror is
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a) ( n-1) f
0%
b) ( n-1)f /n
0%
c)( n+1)f /n
0%
d)(n+1)f
Explanation
Answer: (a)
Q.13
A person standing in the centre of a room, 12 m high looks into a plane mirror fixed on the wall. Then the minimum length of the plane mirror from him to see the full length image of the wall behind him, is equal to
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a)12 m
0%
b) 8 m
0%
c)4 m
0%
d)6 m
Explanation
Answer:(c)
Q.14
It is necessary to illuminate the bottom of well by reflected solar beam when the light is incident at an angle θ=40° to the vertical. At what angle to the horizontal should a plane mirror be placed to do this
0%
a) 70°
0%
b) 20°
0%
c) 50°
0%
d) 40°
Explanation
Answer: (c)
Q.15
A virtual object placed between the pole and the principal focus of a convex mirror produce an real image which is
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a)real, magnified and upright
0%
b) virtual, diminished and inverted
0%
c)virtual, diminished and upright
0%
d)real, diminished and inverted
Explanation
Answer: (a)
Q.16
It is desired to photograph the image of an object placed at a distance of 3m from a plane mirror. The camera, which is at a distance of 4.5m from the mirror should be focaused for a distance of
0%
a) 3 m
0%
b) 4.5 m
0%
c)6 m
0%
d)7.5 m
Explanation
Answer: (d)
Q.17
How many images of himself does an observer see if two adjacent walls of rectangular room are mirror surfaced
0%
a) 3
0%
b) 5
0%
c)7
0%
d)9
Explanation
Answer:(a)
Q.18
Sun subtends an angle of (1/2)° at the centre of curvature of 15m. The size of the image of the sun formed by the mirror is
0%
a) 8.55 cm
0%
b) 7.55 cm
0%
c) 6.55 cm
0%
d) 5.55 cm
Explanation
Answer: (c)
Q.19
A concave mirror of focal length 200cm is used to obtain the image of the sun which subtends an angle of 30'. Then the diameter of the image of the solar disc is
0%
a)3.48 cm
0%
b) 1.74 cm
0%
c)0.87 cm
0%
d)200 cm
Explanation
Answer: (b)
Q.20
A spherical mirror forms diminished virtual image of the magnification 1/Focal length is 18cm. the distance of the object is
0%
a) 18 cm
0%
b) 36 cm
0%
c)48 cm
0%
d)∞
Explanation
Answer: (b)
Q.21
A cubical room is formed with six plane mirrors. An insect moves along the diagonal of the floor with uniform speed. The velocities of its image in two adjacent walls are 20√2 cm/sec, then the velocity of the image formed by the roof is
0%
a) 20 cm/sec
0%
b) 40 cm/sec
0%
c)20√2 cm /sec
0%
d)10√2 cm/sec
Explanation
Answer:(b)
Q.22
The image formed by convex mirror of focal length 30cm is quarter of the size of the object. Then the distance of the object from the mirror is
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a) 30 cm
0%
b) 90 cm
0%
c) 120 cm
0%
d) 60 cm
Explanation
Answer: (b)
Q.23
A convex mirror has a focal length f. A real object is placed at a distance f/2 in front of it from the pole. the mirror produces an image at
0%
a)infinity
0%
b) f
0%
c)2f
0%
d)f/3
Explanation
Answer: (d)
Q.24
Which of the following can not produce a virtual image
0%
a) Plane mirror
0%
b) concave mirror
0%
c)concave lens
0%
d)all of them can produce a virtual image
Explanation
Answer: (d)
Q.25
An object is placed at a distance of 25cm from the pole of convex mirror and plane mirror is set so that the virtual image is formed by the to mirror is 20 cm from the object. the focal length of the mirror is
0%
a) 37.5 cm
0%
b) -7.5 cm
0%
c)-37.5 cm
0%
d)+75 cm
Explanation
Answer:(a)
Q.26
A convex and concave mirror of radii 10 cm each are facing each other and 15cm apart. A point object is placed mid-way between them. Then the position of the final image if the reflection first takes place at the concave mirror is
0%
a) At the pole of concave mirror
0%
b) At the pole of the convex mirror
0%
c) coincident ith the convex mirror
0%
d) none of these
Explanation
Answer: (b)
Q.27
A spherical mirror forms a real image of a point object placed in front. The distance of the image and object from the mirror is 30cm and 0.2 m respectively. The focal length and nature of the mirror are
0%
a)120 mm, concave
0%
b) 120mm, convex
0%
c)60 cm, concave
0%
d)60 cm, convex
Explanation
Answer: (a)
Q.28
A concave mirror of focal length f produces an image n times the size of the object. If the image is real, then the distance of the object from the mirror is
0%
a) (n-1)f
0%
b)(n-1)f / n
0%
c)(n+1)f / n
0%
d)(n+1)f
Explanation
n=v/u v=nu Answer: (c)
Q.29
A thin rod of length f/3 lies along the axis of a concave mirror of focal length f. One end of its image touches the end of the rod. The length of the image is
0%
a) f
0%
b) f/2
0%
c)2f
0%
d)f/4
Explanation
One end lies at the centre of curvature as its image coincides with it. Therefore v2=2fother end of the rod u=2f - f/3=5f/3∴ size of the image=v1 - v2size of the image=f/2 Answer:(b)
Q.30
Thee image of the sun is formed by a concave mirror. the lower half of the mirror is now coated black. Which of the following statement is correct?
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a) the image size is reduced to half
0%
b) the size of the image and intensity remains same
0%
c) the size of the image remains same but it is less intense
0%
d) the size and intensity of the image is reduced to half
Explanation
Answer: (c)
Q.31
The sun has a diameter of 864100 miles and is on an average at a distance of 92900000 miles from the earth. Concave mirror of radius 6 metres is used to obtain its image. the diameter of the image of the solar disc is
0%
a)28 metres
0%
b) 28 cm
0%
c)28 mm
0%
d)28×10-1 mm
Explanation
Image will be at focuses formula I/O=f/uAnswer: (c)
Q.32
Figure shows a cubical room ABCD with wall CD as a plane mirror. Each side of the room is 3m. We place a camera at the mid point of the wall AB. At what distance should the camera be focused to photograph an object placed at A
0%
a) 1.5 cm
0%
b) 3 m
0%
c)6 m
0%
d)more than 6 m
Explanation
ThE image of A is formed 3 m behind the mirror at a point A'. A'A=6m bot OA' > 6 m. There for d is correct option Answer: (d)
Q.33
A ray of light makes an angle of 10° with the horizontal and strikes a plane mirror which is inclined at an angle θ to the horizontal. The angle θ for the reflected ray becomes vertical, is
0%
a) 40°
0%
b) 80°
0%
c)50°
0%
d)100°
Explanation
from the geometry of diagram Answer:(c)
Q.34
A clock hung on a wall has marks instead of numerals in its dial. On the adjoining wall there is a plane mirror and the image of the clock in the mirror indicates the time 4.Then the time on the clock is
0%
a) 7.40
0%
b) 4.20
0%
c) 2.40
0%
d) 4.07
Explanation
Answer: (a)
Q.35
For a convex mirror, the variation of u vs v is given by
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
Answer: (c)
Q.36
A aluminum object is placed 20 cm from the surface of a convex mirror and a plane mirror it set so that the virtual images formed in two mirrors coincides. If the plane mirror is at a distance of 12 cms from the object, then the focal length of the convex mirror is
0%
a) 10 cm
0%
b) 5 cm
0%
c)20 cm
0%
d)40 cm
Explanation
Given that image in plain and mirror and convex mirror coincide. Object is at 12 cm from plain mirror. Thus distance between object and image is 24 Now object is at 20cm from convex mirror thus image must be at 24-20 = 4 cm Now u=-20cm and v = 4 Using mirror equation f= 5cmAnswer: (b)
Q.37
A man wearing yellow coloured glass for left eye and red coloured glass for right eye stand in front of a plane mirror. Which of the following statement is correct?
0%
a) Both eyes are red colour
0%
b) Both eyes are of yellow colour
0%
c)Left eye is yellow coloured and right red
0%
d)Left eye is red and right is yellow
Explanation
Answer:(d)
Q.38
A point object O is placed between two plane mirrors as shown in figure. The distance of the first three images formed by mirror M2 form it are
0%
a) 2 mm, 8 mm, 18 mm
0%
b) 2 mm, 18 mm, 28 mm
0%
c) 2 mm, 18 mm, 22 mm
0%
d) 2 mm, 18 mm, 58 mm
Explanation
Answer: (c)
Q.39
Two plane mirrors M1 and M2 have a length of 2m each and are 10 mm apart. A ray of light is incident on one end of the mirror M2 at an angle of 30°. The number of reflections light undergoes before reaching the other end is
0%
a)170
0%
b) 100
0%
c)150
0%
d)200
Explanation
Answer: (a)
Q.40
A point object is placed at a distance of 500 mm from a concave mirror of focal length 200 mm. If the object is moved towards the mirror by 100 m, the image moves by a distance of
0%
a) 67 mm towards mirror
0%
b) 67 mm away from the mirror
0%
c)10 mm towards mirror
0%
d)10 mm away from the mirror
Explanation
use mirror formula for two object distance and solveAnswer: (b)
Q.41
A candle is placed in front of a concave mirror. The image of candle is formed on wall at a distance of 2m from the candle. The size of the image is 6 times that of the candle. The distance of the candle from the mirror is
0%
a) 1.6 m
0%
b) 2.4 m
0%
c)2.0 m
0%
d)0.4 m
Explanation
Answer:(d)
Q.42
A object is placed at a distance of 2f from a concave mirror. Light reflected from the mirror falls on a plane mirror. The distance of the plane mirror from the concave mirror equals f. The distance of the final image from the concave mirror ( due to reflection at both concave and plane mirror ) is
0%
a) f
0%
b) f/2
0%
c) 2f
0%
d) zero
Explanation
Answer: (d)
Q.43
A concave mirror forms an image one -fourth the size of the object. If object is at a distance of 0.5 m from the mirror, the focal length of mirror is
0%
a)0.16 m
0%
b) -1.5 m
0%
c)0.4 m
0%
d)-0.4 m
Explanation
Answer: (a)
Q.44
A concave mirror of focal length f from an image of the same size as the object. The distance of the object from the mirror is
0%
a) f
0%
b) f/2
0%
c)2f
0%
d)4f
Explanation
Answer: (c)
Q.45
A driver mirror consists of a cylindrical mirror of radius 5cm and the length over the curvered surface is 10cms. If the eye of the driver be assumed to be at a great distance from mirror, then field of view in radian is
0%
a)0.5
0%
b)1.0
0%
c)2.0
0%
d)Indeterminate
Explanation
Image of object at greater distance is formed at focus θ=arc / radius=10/5=2 rad Answer:(c)
Q.46
A concave mirror of focal length 20cms produces an image twice the size of the object. If the image is real, then the distance of the object from the mirror is
0%
a) 20 cm
0%
b) 10 cm
0%
c) 30 cm
0%
d) 60 cm
Explanation
Answer: (c)
Q.47
A concave mirror forms, on a screen a real image of twice the linear dimensions of the object. Object and screen are then moved until the image is three times the size of the object. If the shift of the screen is 25cm, then the focal length of the mirror is
0%
a)5 cm
0%
b) 16.60 cm
0%
c)25 cm
0%
d)37.5 cm
Explanation
Answer: (c)
Q.48
An object infront of plane mirror is displaced by 0.8 m along a straight line at an angle 30° to the mirror plane. The change in the distance between the object and image is
0%
a) 0.20 m
0%
b) 0.40 m
0%
c)0.68 m
0%
d)0.8 m
Explanation
Answer: (d)
Q.49
Light of λ=500nm is travelling in air. Thin glass plate (µ=1.5 ) of thickness 1 mm is placed in the path of light. The change in phase of light is
0%
a) zero
0%
b) π/2
0%
c)π
0%
d)3π/2
Explanation
Answer:(a)
Q.50
A bird in air looks at fish vertically below it and inside water X is the height of the bird above the surface of water and Y the depth of the fish below the surface of water. If the refractive index of water with respect to air is µ, the distance of the fish as observed by the bird is
0%
a) X + Y
0%
b) X + (Y/µ)
0%
c) µX + Y
0%
d) µX + µY
Explanation
Apparent depth of the fish as observed by the bird µ=real depth / Apparent depth Add apparent depth with height of bird from water surface Answer: (b)
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