DPP for NEET: Daily Practice Problems, Ch 51: Ray Optics- 3 | Physics Class 12 PDF Download

 Page 1


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A small point object is placed at O, at a distance of 0.60
metre in air from a convex spherical surface of refractive
index 1.5. If the radius of the curvature is 25 cm, then what
is the position of the image on the principal axis ?
(a) 4.5 m (b) 2.5 m
(c) 1.5 m (d) 5.5 m
Q.2 The radius of a glass ball is 5 cm. There is an air bubble at
1cm from the centre of the ball and refractive index of
glass is 1.5. The position of image viewed from surface
near the bubble is.
(a) 3.63 cm (b) 4.63 cm
(c) 2.12 cm (d) 5.12 cm
Q.3 In case of thin lens of focal length f  an object is placed at
a distance x
1
 from first focus and its image is formed at a
distance x
2
 from the second focus, find x
1
 x
2
(a)f (b) f 
3
(c) f 
2
(d) 1/f
Q.4 What is the  refractive index of material of a plano-convex
lens , if the radius of curvature of the convex surface is
10 cm and focal length of the lens is 30 cm ?
(a) 1/3 (b) 4/3
(c) 2/3 (d) 1/4
Q.5 A convex lens of focal length 10.0 cm is placed in contact
with a convex lens of 15.0 cm focal length. What is the
focal length of the combination ?
(a) 6 cm (b) 12 cm
(c) 8 cm (d) 4 cm
Page 2


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A small point object is placed at O, at a distance of 0.60
metre in air from a convex spherical surface of refractive
index 1.5. If the radius of the curvature is 25 cm, then what
is the position of the image on the principal axis ?
(a) 4.5 m (b) 2.5 m
(c) 1.5 m (d) 5.5 m
Q.2 The radius of a glass ball is 5 cm. There is an air bubble at
1cm from the centre of the ball and refractive index of
glass is 1.5. The position of image viewed from surface
near the bubble is.
(a) 3.63 cm (b) 4.63 cm
(c) 2.12 cm (d) 5.12 cm
Q.3 In case of thin lens of focal length f  an object is placed at
a distance x
1
 from first focus and its image is formed at a
distance x
2
 from the second focus, find x
1
 x
2
(a)f (b) f 
3
(c) f 
2
(d) 1/f
Q.4 What is the  refractive index of material of a plano-convex
lens , if the radius of curvature of the convex surface is
10 cm and focal length of the lens is 30 cm ?
(a) 1/3 (b) 4/3
(c) 2/3 (d) 1/4
Q.5 A convex lens of focal length 10.0 cm is placed in contact
with a convex lens of 15.0 cm focal length. What is the
focal length of the combination ?
(a) 6 cm (b) 12 cm
(c) 8 cm (d) 4 cm
2
DPP/ P 51
Q.6 A convex lens of focal length 20 cm is placed in contact
with a diverging lens of unknown focal length. The lens
combination acts as a converging lens and has a focal length
of 30 cm. What is the focal length of the diverging lens ?
(a) – 10 cm (b) – 30 cm (c) – 60 cm (d) – 90 cm
Q.7 A pin is placed 10 cm in front of a convex lens of focal
length 20 cm, made of material having refractive index 1.5.
The surface of the lens farther away from the pin is silvered
and has a radius of curvature 22 cm. Determine the position
of the final image.
(a) 11 cm in front (b) 21 cm in front
(c) 15 cm in front (d) 31 cm in front
Q.8 An image is formed on the screen by a convex lens. When
upper half part of lens is covered with black paper, then :
(a) half image is formed
(b) full image is formed
(c) intensity of image will be enhanced
(d) None of these
Q.9 A convex lens is made out of a substance of 1.2 refractive
index. The two surfaces of lens are convex. If this lens is
placed in water whose refractive index is 1.33, it will
behave as :
(a) convergent lens (b) divergent lens
(c) plane glass plate (d) like a prism
Q.10 An equiconvex lens has a power of 5 diopter. If it  is made
of glass of refractive index 1.5 then the radius of the
curvature of each surface will be
(a) 20 cm (b) 10 cm (c) 5 cm (d) zero
Q.11 A convex lens when placed in the first position forms a
real image of an object on a fixed screen. The distance
between the object and the screen is 75 cm. On displacing
the lens from first position by 25 cm to the second position,
again a real image is formed on the screen. Then the focal
length of the lens is
D = 75 cm
x = 25 cm
I
2
I
1
Second position
First position
Object
(a) 25.0 cm (b) 16.7 cm (c) 50.3 cm (d) 33.3 cm
Q.12 A lens is placed between a source of light and a wall. It
forms images of area A
1
 and A
2
 on the wall for its two
different positions. The area of the source of light is
(a)
12
A +A
2
(b)
1
12
11
AA
-
éù
+
êú
ëû
(c)
12
AA (d)
2
12
AA
2
éù
+
êú
êú
ëû
Q.13 A convex lens of power 4D is kept in contact with a concave
lens of power 3D, the effective power of combination will
be
(a) 7D (b) 4D/3
(c) 1D (d) 3D/4
Q.14 The power of a plano-convex lens is P. If this lens is cut
longitudinally along its principal axis into two equal parts
and then they are joined as given in the figure. The power
of combination will be :
(a)P
(b) 2P
(c) P/2
(d) zero
Q.15The plane surface of a planoconvex lens is silvered. If
ra dius o f curve d s urfa ce is R a nd re fra ctive inde x is m, then
the system behaves like a concave mirror whose radius
will be
(a)
R
m
(b)Rm
(c)
R
1 m-
(d) R (m – 1)
Q.16 A slide projector lens has a focal length 10 cm. It throws
an image of a 2cm × 2 cm slide on a screen 5 m from the
lens. Find the size of the picture on the screen.
(a) ( 98 × 98) cm
2
(b) (88 × 88) cm
2
(c) (64 × 64) cm
2
(d) (78 × 78) cm
2
Q.17If the focal length of a magnifier is 5 cm calculate the
power of the lens.
(a) 20D (b) 10D
(c) 5D (d) 15D
Page 3


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A small point object is placed at O, at a distance of 0.60
metre in air from a convex spherical surface of refractive
index 1.5. If the radius of the curvature is 25 cm, then what
is the position of the image on the principal axis ?
(a) 4.5 m (b) 2.5 m
(c) 1.5 m (d) 5.5 m
Q.2 The radius of a glass ball is 5 cm. There is an air bubble at
1cm from the centre of the ball and refractive index of
glass is 1.5. The position of image viewed from surface
near the bubble is.
(a) 3.63 cm (b) 4.63 cm
(c) 2.12 cm (d) 5.12 cm
Q.3 In case of thin lens of focal length f  an object is placed at
a distance x
1
 from first focus and its image is formed at a
distance x
2
 from the second focus, find x
1
 x
2
(a)f (b) f 
3
(c) f 
2
(d) 1/f
Q.4 What is the  refractive index of material of a plano-convex
lens , if the radius of curvature of the convex surface is
10 cm and focal length of the lens is 30 cm ?
(a) 1/3 (b) 4/3
(c) 2/3 (d) 1/4
Q.5 A convex lens of focal length 10.0 cm is placed in contact
with a convex lens of 15.0 cm focal length. What is the
focal length of the combination ?
(a) 6 cm (b) 12 cm
(c) 8 cm (d) 4 cm
2
DPP/ P 51
Q.6 A convex lens of focal length 20 cm is placed in contact
with a diverging lens of unknown focal length. The lens
combination acts as a converging lens and has a focal length
of 30 cm. What is the focal length of the diverging lens ?
(a) – 10 cm (b) – 30 cm (c) – 60 cm (d) – 90 cm
Q.7 A pin is placed 10 cm in front of a convex lens of focal
length 20 cm, made of material having refractive index 1.5.
The surface of the lens farther away from the pin is silvered
and has a radius of curvature 22 cm. Determine the position
of the final image.
(a) 11 cm in front (b) 21 cm in front
(c) 15 cm in front (d) 31 cm in front
Q.8 An image is formed on the screen by a convex lens. When
upper half part of lens is covered with black paper, then :
(a) half image is formed
(b) full image is formed
(c) intensity of image will be enhanced
(d) None of these
Q.9 A convex lens is made out of a substance of 1.2 refractive
index. The two surfaces of lens are convex. If this lens is
placed in water whose refractive index is 1.33, it will
behave as :
(a) convergent lens (b) divergent lens
(c) plane glass plate (d) like a prism
Q.10 An equiconvex lens has a power of 5 diopter. If it  is made
of glass of refractive index 1.5 then the radius of the
curvature of each surface will be
(a) 20 cm (b) 10 cm (c) 5 cm (d) zero
Q.11 A convex lens when placed in the first position forms a
real image of an object on a fixed screen. The distance
between the object and the screen is 75 cm. On displacing
the lens from first position by 25 cm to the second position,
again a real image is formed on the screen. Then the focal
length of the lens is
D = 75 cm
x = 25 cm
I
2
I
1
Second position
First position
Object
(a) 25.0 cm (b) 16.7 cm (c) 50.3 cm (d) 33.3 cm
Q.12 A lens is placed between a source of light and a wall. It
forms images of area A
1
 and A
2
 on the wall for its two
different positions. The area of the source of light is
(a)
12
A +A
2
(b)
1
12
11
AA
-
éù
+
êú
ëû
(c)
12
AA (d)
2
12
AA
2
éù
+
êú
êú
ëû
Q.13 A convex lens of power 4D is kept in contact with a concave
lens of power 3D, the effective power of combination will
be
(a) 7D (b) 4D/3
(c) 1D (d) 3D/4
Q.14 The power of a plano-convex lens is P. If this lens is cut
longitudinally along its principal axis into two equal parts
and then they are joined as given in the figure. The power
of combination will be :
(a)P
(b) 2P
(c) P/2
(d) zero
Q.15The plane surface of a planoconvex lens is silvered. If
ra dius o f curve d s urfa ce is R a nd re fra ctive inde x is m, then
the system behaves like a concave mirror whose radius
will be
(a)
R
m
(b)Rm
(c)
R
1 m-
(d) R (m – 1)
Q.16 A slide projector lens has a focal length 10 cm. It throws
an image of a 2cm × 2 cm slide on a screen 5 m from the
lens. Find the size of the picture on the screen.
(a) ( 98 × 98) cm
2
(b) (88 × 88) cm
2
(c) (64 × 64) cm
2
(d) (78 × 78) cm
2
Q.17If the focal length of a magnifier is 5 cm calculate the
power of the lens.
(a) 20D (b) 10D
(c) 5D (d) 15D
DPP/ P 51
3
Q.18In the above question, find the magnifying power of the
lens for relaxed and strained eye.
(a) 2×, 3× (b) 5×, 6×
(c) 4×, 2× (d) 1×, 2×
Q.19A 35 mm film is to be projected on a 20 m wide screen
situated at a distance of 40 m from the film-projector.
Calculate the focal length of projection lens.
(a) 70 mm (b) 35 mm
(c) 40 mm (d) 20 mm
Q.20 In a compound microscope the objective and the eye- piece
have focal lengths of 0.95 cm and 5 cm respectively, and
are kept at a distance of 20 cm. The last image is formed at
a distance of 25 cm from the eye- piece. Calculate the
total magnification.
(a) 94 (b) 84
(c) 75 (d) 88
Q.21A Galilean telescope consists of an objective of focal
length 12 cm and eye- piece of focal length 4 cm. What
should be the separation of the two lenses when the virtual
image of a distant object is formed at a distance of 24 cm
from the eye- piece?
(a) 7.2 cm (b) 8.2 cm.
(c) 12.4 cm. (d) 2.8cm.
DIRECTIONS (Q.22-Q.24) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.22An astronomical telescope has an angular magnification
of magnitude 5 for distant objects. The separation between
the objective and eye- piece is 36 cm and the final image
is formed at infinity.
(1) the focal length of objective is 30 cm
(2) the focal length of objective is 25 cm
(3) the focal length of eye piece is 6 cm
(4) the focal length of eye piece is 12 cm
Q.23Resolving power of a microscope doesn't depend upon
(1) Velocity of light used
(2) Frequency of light used
(3) Focal length of objective
(4) Wavelength of light used
Q.24The light gathering power of a camera lens
doesn't depend on
(1) Ratio of focal length and diameter
(2) Product of focal length and diameter
(3) Wavelength of light used
(4) Its diameter
DIRECTIONS (Q.25-Q.27) : Read the passage given below
and answer the questions that follows :
L
2
L
1
m
1
m
2
m
w
O
A cylindrical tube filled with water (µ
w
 = 4/3) is closed at its
both ends by two silvered plano convex lenses as shown in the
figure. R efra ctive index o f lenses L
1
 and L
2
 are 2.0 and 1.5 while
their radii of curvature are 5 cm and 9 cm respectively. A point
object is placed somewhere at a point O on the axis of cylindrical
tube. It is found that the object and image coincide each other.
Q.25 The position of object w.r.t lens L
1
 is
(a) 8 cm (b) 10 cm
(c) 12 cm (d) 14 cm
Q.26 The position of object w.r.t lens L
2
 is
(a) 8 cm (b) 10 cm
(c) 12 cm (d) 14 cm
Q.27 The length of the cylindrical tube is
(a) 16 cm (b) 18 cm
(c) 20 cm (d) 22 cm
Page 4


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A small point object is placed at O, at a distance of 0.60
metre in air from a convex spherical surface of refractive
index 1.5. If the radius of the curvature is 25 cm, then what
is the position of the image on the principal axis ?
(a) 4.5 m (b) 2.5 m
(c) 1.5 m (d) 5.5 m
Q.2 The radius of a glass ball is 5 cm. There is an air bubble at
1cm from the centre of the ball and refractive index of
glass is 1.5. The position of image viewed from surface
near the bubble is.
(a) 3.63 cm (b) 4.63 cm
(c) 2.12 cm (d) 5.12 cm
Q.3 In case of thin lens of focal length f  an object is placed at
a distance x
1
 from first focus and its image is formed at a
distance x
2
 from the second focus, find x
1
 x
2
(a)f (b) f 
3
(c) f 
2
(d) 1/f
Q.4 What is the  refractive index of material of a plano-convex
lens , if the radius of curvature of the convex surface is
10 cm and focal length of the lens is 30 cm ?
(a) 1/3 (b) 4/3
(c) 2/3 (d) 1/4
Q.5 A convex lens of focal length 10.0 cm is placed in contact
with a convex lens of 15.0 cm focal length. What is the
focal length of the combination ?
(a) 6 cm (b) 12 cm
(c) 8 cm (d) 4 cm
2
DPP/ P 51
Q.6 A convex lens of focal length 20 cm is placed in contact
with a diverging lens of unknown focal length. The lens
combination acts as a converging lens and has a focal length
of 30 cm. What is the focal length of the diverging lens ?
(a) – 10 cm (b) – 30 cm (c) – 60 cm (d) – 90 cm
Q.7 A pin is placed 10 cm in front of a convex lens of focal
length 20 cm, made of material having refractive index 1.5.
The surface of the lens farther away from the pin is silvered
and has a radius of curvature 22 cm. Determine the position
of the final image.
(a) 11 cm in front (b) 21 cm in front
(c) 15 cm in front (d) 31 cm in front
Q.8 An image is formed on the screen by a convex lens. When
upper half part of lens is covered with black paper, then :
(a) half image is formed
(b) full image is formed
(c) intensity of image will be enhanced
(d) None of these
Q.9 A convex lens is made out of a substance of 1.2 refractive
index. The two surfaces of lens are convex. If this lens is
placed in water whose refractive index is 1.33, it will
behave as :
(a) convergent lens (b) divergent lens
(c) plane glass plate (d) like a prism
Q.10 An equiconvex lens has a power of 5 diopter. If it  is made
of glass of refractive index 1.5 then the radius of the
curvature of each surface will be
(a) 20 cm (b) 10 cm (c) 5 cm (d) zero
Q.11 A convex lens when placed in the first position forms a
real image of an object on a fixed screen. The distance
between the object and the screen is 75 cm. On displacing
the lens from first position by 25 cm to the second position,
again a real image is formed on the screen. Then the focal
length of the lens is
D = 75 cm
x = 25 cm
I
2
I
1
Second position
First position
Object
(a) 25.0 cm (b) 16.7 cm (c) 50.3 cm (d) 33.3 cm
Q.12 A lens is placed between a source of light and a wall. It
forms images of area A
1
 and A
2
 on the wall for its two
different positions. The area of the source of light is
(a)
12
A +A
2
(b)
1
12
11
AA
-
éù
+
êú
ëû
(c)
12
AA (d)
2
12
AA
2
éù
+
êú
êú
ëû
Q.13 A convex lens of power 4D is kept in contact with a concave
lens of power 3D, the effective power of combination will
be
(a) 7D (b) 4D/3
(c) 1D (d) 3D/4
Q.14 The power of a plano-convex lens is P. If this lens is cut
longitudinally along its principal axis into two equal parts
and then they are joined as given in the figure. The power
of combination will be :
(a)P
(b) 2P
(c) P/2
(d) zero
Q.15The plane surface of a planoconvex lens is silvered. If
ra dius o f curve d s urfa ce is R a nd re fra ctive inde x is m, then
the system behaves like a concave mirror whose radius
will be
(a)
R
m
(b)Rm
(c)
R
1 m-
(d) R (m – 1)
Q.16 A slide projector lens has a focal length 10 cm. It throws
an image of a 2cm × 2 cm slide on a screen 5 m from the
lens. Find the size of the picture on the screen.
(a) ( 98 × 98) cm
2
(b) (88 × 88) cm
2
(c) (64 × 64) cm
2
(d) (78 × 78) cm
2
Q.17If the focal length of a magnifier is 5 cm calculate the
power of the lens.
(a) 20D (b) 10D
(c) 5D (d) 15D
DPP/ P 51
3
Q.18In the above question, find the magnifying power of the
lens for relaxed and strained eye.
(a) 2×, 3× (b) 5×, 6×
(c) 4×, 2× (d) 1×, 2×
Q.19A 35 mm film is to be projected on a 20 m wide screen
situated at a distance of 40 m from the film-projector.
Calculate the focal length of projection lens.
(a) 70 mm (b) 35 mm
(c) 40 mm (d) 20 mm
Q.20 In a compound microscope the objective and the eye- piece
have focal lengths of 0.95 cm and 5 cm respectively, and
are kept at a distance of 20 cm. The last image is formed at
a distance of 25 cm from the eye- piece. Calculate the
total magnification.
(a) 94 (b) 84
(c) 75 (d) 88
Q.21A Galilean telescope consists of an objective of focal
length 12 cm and eye- piece of focal length 4 cm. What
should be the separation of the two lenses when the virtual
image of a distant object is formed at a distance of 24 cm
from the eye- piece?
(a) 7.2 cm (b) 8.2 cm.
(c) 12.4 cm. (d) 2.8cm.
DIRECTIONS (Q.22-Q.24) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.22An astronomical telescope has an angular magnification
of magnitude 5 for distant objects. The separation between
the objective and eye- piece is 36 cm and the final image
is formed at infinity.
(1) the focal length of objective is 30 cm
(2) the focal length of objective is 25 cm
(3) the focal length of eye piece is 6 cm
(4) the focal length of eye piece is 12 cm
Q.23Resolving power of a microscope doesn't depend upon
(1) Velocity of light used
(2) Frequency of light used
(3) Focal length of objective
(4) Wavelength of light used
Q.24The light gathering power of a camera lens
doesn't depend on
(1) Ratio of focal length and diameter
(2) Product of focal length and diameter
(3) Wavelength of light used
(4) Its diameter
DIRECTIONS (Q.25-Q.27) : Read the passage given below
and answer the questions that follows :
L
2
L
1
m
1
m
2
m
w
O
A cylindrical tube filled with water (µ
w
 = 4/3) is closed at its
both ends by two silvered plano convex lenses as shown in the
figure. R efra ctive index o f lenses L
1
 and L
2
 are 2.0 and 1.5 while
their radii of curvature are 5 cm and 9 cm respectively. A point
object is placed somewhere at a point O on the axis of cylindrical
tube. It is found that the object and image coincide each other.
Q.25 The position of object w.r.t lens L
1
 is
(a) 8 cm (b) 10 cm
(c) 12 cm (d) 14 cm
Q.26 The position of object w.r.t lens L
2
 is
(a) 8 cm (b) 10 cm
(c) 12 cm (d) 14 cm
Q.27 The length of the cylindrical tube is
(a) 16 cm (b) 18 cm
(c) 20 cm (d) 22 cm
4
DPP/ P 51
DIRECTIONS (Q. 28-Q.30) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q.28 Statement-1: A double convex lens (m = 1.5) has focal
length 10 cm. When the lens is immersed in water  ( m = 4/
3) its focal length becomes 40 cm.
Statement-2: 
12
1 11 æö m -m
=-
ç÷
m èø
lm
m
f RR
Q.29 Statement-1: The focal length of lens changes when red
light is replaced by blue light.
Statement-2: The focal length of lens does not depend on
colour of light used.
Q.30 Statement-1: By increasing the diameter of the objective
of telescope, we can increase its range.
Statement-2: The range of a telescope tells us how far
away a star of some standard brightness can be spotted by
telescope.