12583 + Mcqs in Physics Page 235 McqOptions

11701.	The index of refraction of diamond is 2.0, velocity of light in diamond in cm/second is approximately [CPMT 1975; MNR 1987; UPSEAT 2000]
A.	\[6\times {{10}^{10}}\]
B.	\[3.0\times {{10}^{10}}\]
C.	\[2\times {{10}^{10}}\]
D.	\[1.5\times {{10}^{10}}\]
Answer» E.

Discussion

11702.	Refractive index for a material for infrared light is [CPMT 1984]
A.	Equal to that of ultraviolet light
B.	Less than for ultraviolet light
C.	Equal to that for red colour of light
D.	Greater than that for ultraviolet light
Answer» C. Equal to that for red colour of light

Discussion

11703.	Figure given below shows a beam of light converging at point P. When a convex lens of focal length 16 cm is introduced in the path of the beam at a place O shown by dotted line such that OP becomes the axis of the lens, the beam converges at a distance x from the lens. The value x will be equal to [AMU (Med.) 2002]
A.	12 cm
B.	24 cm
C.	36 cm
D.	48 cm
Answer» E.

Discussion

11704.	A thin lens made of glass of refractive index m = 1.5 has a focal length equal to 12 cm in air. It is now immersed in water \[\left( \mu \,=\,\frac{4}{3} \right)\]. Its new focal length is [UPSEAT 2002]
A.	48 cm
B.	36 cm
C.	24 cm
D.	12 cm
Answer» B. 36 cm

Discussion

11705.	The unit of focal power of a lens is [KCET 2001]
A.	Watt
B.	Horse power
C.	Dioptre
D.	Lux
Answer» D. Lux

Discussion

11706.	The combination of a convex lens (f = 18 cm) and a thin concave lens (f = 9 cm) is [AMU (Engg.) 2001]
A.	A concave lens (f = 18 cm)
B.	A convex lens (f = 18 cm)
C.	A convex lens (f = 6 cm)
D.	A concave lens (f = 6 cm)
Answer» B. A convex lens (f = 18 cm)

Discussion

11707.	An object has image thrice of its original size when kept at 8 cm and 16 cm from a convex lens. Focal length of the lens is [UPSEAT 2001]
A.	8 cm
B.	16 cm
C.	Between 8 cm and 16 cm
D.	Less than 8 cm
Answer» D. Less than 8 cm

Discussion

11708.	A convex lens has a focal length f. It is cut into two parts along the dotted line as shown in the figure. The focal length of each part will be [MP PET 2000]
A.	\[\frac{f}{2}\]
B.	f
C.	\[\frac{3}{2}f\]
D.	2f
Answer» E.

Discussion

11709.	Chromatic aberration of lens can be corrected by [AFMC 2000]
A.	Reducing its aperature
B.	Proper polishing of its two surfaces
C.	Suitably combining it with another lens
D.	Providing different suitable curvature to its two surfaces
Answer» D. Providing different suitable curvature to its two surfaces

Discussion

11710.	A lens of power + 2 diopters is placed in contact with a lens of power ? 1 diopoter. The combination will behave like [UPSEAT 2000]
A.	A divergent lens of focal length 50 cm
B.	A convergent lens of focal length 50 cm
C.	A convergent lens of focal length 100 cm
D.	A divergent lens of focal length 100 cm
Answer» D. A divergent lens of focal length 100 cm

Discussion

11711.	A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a liquid of refractive index 1.63 is [UPSEAT 2000; Pb. PET 2004]
A.	- 407 cm
B.	250 cm
C.	125 cm
D.	25 cm
Answer» B. 250 cm

Discussion

11712.	A lens of focal power 0.5 D is [JIPMER 1999]
A.	A convex lens of focal length 0.5 m
B.	A concave lens of focal length 0.5 m
C.	A convex lens of focal length 2 m
D.	A concave lens of focal length 2 m
Answer» D. A concave lens of focal length 2 m

Discussion

11713.	A double convex lens of glass of m = 1.5 has radius of curvature of each of its surface is 0.2 m. The power of the lens is [JIPMER 1999]
A.	+ 10 dioptres
B.	- 10 dioptres
C.	- 5 dioptres
D.	+5 dioptres
Answer» E.

Discussion

11714.	A convex lens of power + 6D is placed in contact with a concave lens of power ? 4D. What is the nature and focal length of the combination [AMU (Engg.) 1999]
A.	Concave, 25 cm
B.	Convex, 50 cm
C.	Concave, 20 cm
D.	Convex, 100 cm
Answer» C. Concave, 20 cm

Discussion

11715.	If a lens is cut into two pieces perpendicular to the principal axis and only one part is used, the intensity of the image [CPMT 1996]
A.	Remains same
B.	\[\frac{1}{2}\] times
C.	2 times
D.	Infinite
Answer» B. \[\frac{1}{2}\] times

Discussion

11716.	\[{{f}_{v}}\]and \[{{f}_{r}}\] are the focal lengths of a convex lens for violet and red light respectively and \[{{F}_{v}}\] and \[{{F}_{r}}\]are the focal lengths of a concave lens for violet and red light respectively, then [CBSE PMT 1996]
A.	\[{{f}_{v}}<{{f}_{r}}\] and \[{{F}_{v}}>{{F}_{r}}\]
B.	\[{{f}_{v}}<{{f}_{R}}\] and \[{{F}_{v}}<{{F}_{r}}\]
C.	\[{{f}_{c}}>{{f}_{r}}\] and \[{{F}_{v}}>{{F}_{r}}\]
D.	\[{{f}_{v}}>{{f}_{r}}\] and \[{{F}_{v}}<{{F}_{r}}\]
Answer» C. \[{{f}_{c}}>{{f}_{r}}\] and \[{{F}_{v}}>{{F}_{r}}\]

Discussion

11717.	If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power [CBSE PMT 1996; AFMC 2002]
A.	+ 6.5D
B.	- 6.5 D
C.	+ 7.5 D
D.	- 0.75 D
Answer» E.

Discussion

11718.	A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a [IIT-JEE 1999]
A.	Convergent lens of focal length 3.5 R
B.	Convergent lens of focal length 3.0 R
C.	Divergent lens of focal length 3.5 R
D.	Divergent lens of focal length 3.0 R
Answer» B. Convergent lens of focal length 3.0 R

Discussion

11719.	A plane convex lens is made of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is [CBSE PMT 1999; Pb. PMT 1999; BHU 2001; Very Similar to BHU 2003]
A.	50 cm
B.	100 cm
C.	200 cm
D.	400 cm
Answer» C. 200 cm

Discussion

11720.	A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power of a cut lens will be [MP PMT 1999]
A.	2 D
B.	3 D
C.	4 D
D.	5 D
Answer» B. 3 D

Discussion

11721.	Two lenses are placed in contact with each other and the focal length of combination is 80 cm. If the focal length of one is 20 cm, then the power of the other will be [NCERT 1981]
A.	1.66 D
B.	4.00 D
C.	-1.00 D
D.	- 3.75 D
Answer» E.

Discussion

11722.	A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of combination is [IIT-JEE 1982; AFMC 1997; CBSE PMT 2000; RPMT 2003]
A.	- 1.5 D
B.	- 6.5 D
C.	+ 6.5 D
D.	+ 6.67 D
Answer» B. - 6.5 D

Discussion

11723.	A lens of power + 2 diopters is placed in contact with a lens of power - 1 diopter. The combination will behave like
A.	A convergent lens of focal length 50 cm
B.	A divergent lens of focal length 100 cm
C.	A convergent lens of focal length 100 cm
D.	A convergent lens of focal length 200 cm
Answer» D. A convergent lens of focal length 200 cm

Discussion

11724.	A lens (focal length 50 cm) forms the image of a distant object which subtends an angle of 1 milliradian at the lens. What is the size of the image [MP PMT 1995]
A.	5 mm
B.	1 mm
C.	0.5 mm
D.	0.1 mm
Answer» D. 0.1 mm

Discussion

11725.	In the figure, an air lens of radii of curvature 10 cm (\[{{R}_{1}}\] = \[{{R}_{2}}\] = 10 cm) is cut in a cylinder of glass\[(\mu =1.5)\]. The focal length and the nature of the lens is [MP PET 1995; Pb. PET 2000]
A.	15 cm, concave
B.	15 cm, convex
C.	\[\infty \], neither concave nor convex
D.	0, concave
Answer» B. 15 cm, convex

Discussion

11726.	A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black, the image will [MP PET 1995]
A.	Be shifted downwards
B.	Be shifted upwards
C.	Not be shifted
D.	Shift on the principal axis
Answer» D. Shift on the principal axis

Discussion

11727.	A diminished image of an object is to be obtained on a screen 1.0 m from it. This can be achieved by appropriately placing [IIT JEE 1995]
A.	A convex mirror of suitable focal length
B.	A concave mirror of suitable focal length
C.	A concave lens of suitable focal length
D.	A convex lens of suitable focal length less than 0.25 m
Answer» E.

Discussion

11728.	If the central portion of a convex lens is wrapped in black paper as shown in the figure [Manipal MEE 1995; KCET 2001]
A.	No image will be formed by the remaining portion of the lens
B.	The full image will be formed but it will be less bright
C.	The central portion of the image will be missing
D.	There will be two images each produced by one of the exposed portions of the lens
Answer» C. The central portion of the image will be missing

Discussion

11729.	A plano convex lens \[(f=20cm)\]is silvered at plane surface. Now f will be [BHU 1995; DPMT 2001; MP PMT 2005]
A.	20 cm
B.	40 cm
C.	30 cm
D.	10 cm
Answer» E.

Discussion

11730.	Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact convex. The effective power of the combination is [CBSE PMT 1990; RPMT 2001]
A.	45 dioptres
B.	9 dioptres
C.	1/9 dioptre
D.	6 dioptres
Answer» C. 1/9 dioptre

Discussion

11731.	A double convex lens of focal length 20 cm is made of glass of refractive index 3 / 2. When placed completely in water \[{{(}_{a}}{{\mu }_{w}}=4/3)\], its focal length will be [CBSE PMT 1990; MP PMT/PET 1998]
A.	80 cm
B.	15 cm
C.	17.7 cm
D.	22.5 cm
Answer» B. 15 cm

Discussion

11732.	Two thin lenses, one of focal length + 60 cm and the other of focal length -20 cm are put in contact. The combined focal length is [CPMT 1973, 89; BVP 2003]
A.	+ 15 cm
B.	-15 cm
C.	+ 30 cm
D.	-30 cm
Answer» E.

Discussion

11733.	A divergent lens will produce [CPMT 1984]
A.	Always a virtual image
B.	Always real image
C.	Sometimes real and sometimes virtual
D.	None of the above
Answer» B. Always real image

Discussion

11734.	A convex lens of crown glass (\[n\]=1.525) will behave as a divergent lens if immersed in [CPMT 1984]
A.	Water (n =1.33)
B.	In a medium of n = 1.525
C.	Carbon disulphide n =1.66
D.	It cannot act as a divergent lens
Answer» D. It cannot act as a divergent lens

Discussion

11735.	If \[{{I}_{1}}\] and \[{{I}_{2}}\] be the size of the images respectively for the two positions of lens in the displacement method, then the size of the object is given by [CPMT 1988]
A.	\[{{I}_{1}}/{{I}_{2}}\]
B.	\[{{I}_{1}}\times {{I}_{2}}\]
C.	\[\sqrt{{{I}_{1}}\times {{I}_{2}}}\]
D.	\[\sqrt{{{I}_{1}}/{{I}_{2}}}\]
Answer» D. \[\sqrt{{{I}_{1}}/{{I}_{2}}}\]

Discussion

11736.	A glass lens is placed in a medium in which it is found to behave like a glass plate. Refractive index of the medium will be [CPMT 1981, 84, 85]
A.	Greater than the refractive index of glass
B.	Smaller than the refractive index of glass
C.	Equal to refractive index of glass
D.	No case will be possible from above
Answer» D. No case will be possible from above

Discussion

11737.	A thin convex lens of refractive index 1.5 has a focal length of 15 cm in air. When the lens is placed in liquid of refractive index 4/3 , its focal length will be [CPMT 1974, 77; MP PMT 1992]
A.	15 cm
B.	10 cm
C.	30 cm
D.	60 cm
Answer» E.

Discussion

11738.	The ray diagram could be correct [CPMT 1988]
A.	If \[{{n}_{1}}={{n}_{2}}={{n}_{g}}\]
B.	If \[{{n}_{1}}={{n}_{2}}\] and \[{{n}_{1}}<{{n}_{g}}\]
C.	If \[{{n}_{1}}={{n}_{2}}\] and \[{{n}_{1}}>{{n}_{g}}\]
D.	Under no circumstances
Answer» D. Under no circumstances

Discussion

11739.	A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths [IIT-JEE (Screening) 2005]
A.	? 75, 50
B.	? 10, 15
C.	75, 50
D.	? 15, 10
Answer» E.

Discussion

11740.	When light rays from the sun fall on a convex lens along a direction parallel to its axis [MP PMT 2004]
A.	Focal length for all colours is the same
B.	Focal length for violet colour is the shortest
C.	Focal length for yellow colour is the longest
D.	Focal length for red colour is the shortest
Answer» C. Focal length for yellow colour is the longest

Discussion

11741.	Two lenses of power + 12 and ? 2 diopters are placed in contact. The combined focal length of the combination will be [Pb. PET 2004]
A.	8.33 cm
B.	1.66 cm
C.	12.5 cm
D.	10 cm
Answer» E.

Discussion

11742.	The focal lengths of convex lens for red and blue light are 100 cm and 96.8 cm respectively. The dispersive power of material of lens is [Pb. PET 2003]
A.	0.325
B.	0.0325
C.	0.98
D.	0.968
Answer» C. 0.98

Discussion

11743.	Spherical aberration in a lens [UPSEAT 2004]
A.	Is minimum when most of the deviation is at the first surface
B.	Is minimum when most of the deviation is at the second surface
C.	Is minimum when the total deviation is equally distributed over the two surface
D.	Does not depend on the above consideration
Answer» D. Does not depend on the above consideration

Discussion

11744.	A bi-convex lens made of glass (refractive index 1.5) is put in a liquid of refractive index 1.7. Its focal length will [UPSEAT 2004]
A.	Decrease and change sign
B.	Increase and change sign
C.	Decrease and remain of the same sign
D.	Increase and remain of the same sign
Answer» C. Decrease and remain of the same sign

Discussion

11745.	A convex lens of focal length 84 cm is in contact with a concave lens of focal length 12 cm. The power of combination (in diopters) is [MP PET 1991]
A.	25/24
B.	25/18
C.	- 50/7
D.	7.14285714285714
Answer» C. - 50/7

Discussion

11746.	A thin convex lens of focal length 10 cm is placed in contact with a concave lens of same material and of same focal length. The focal length of combination will be [CPMT 1972; 1988]
A.	Zero
B.	Infinity
C.	10 cm
D.	20 cm
Answer» C. 10 cm

Discussion

11747.	A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen [IIT-JEE 1986; SCRA 1994; MP PET 1996; MP PMT 2004; BHU 1998, 05]
A.	Half the image will disappear
B.	Complete image will be formed of same intensity
C.	Half image will be formed of same intensity
D.	Complete image will be formed of decreased intensity
Answer» E.

Discussion

11748.	The radius of the convex surface of plano-convex lens is 20 cm and the refractive index of the material of the lens is 1.5. The focal length of the lens is [CPMT 2004]
A.	30 cm
B.	50 cm
C.	20 cm
D.	40 cm
Answer» E.

Discussion

11749.	A combination of two thin convex lenses of focal length 0.3 m and 0.1 m will have minimum spherical and chromatic aberrations if the distance between them is [UPSEE 2004]
A.	0.1 m
B.	0.2 m
C.	0.3 m
D.	0.4 m
Answer» C. 0.3 m

Discussion

11750.	A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is [Pb. PET 2000]
A.	400 cm
B.	200 cm
C.	100 cm
D.	50 cm
Answer» D. 50 cm

Discussion

Explore topic-wise MCQs in Joint Entrance Exam - Main (JEE Main).

The index of refraction of diamond is 2.0, velocity of light in diamond in cm/second is approximately [CPMT 1975; MNR 1987; UPSEAT 2000]

Refractive index for a material for infrared light is [CPMT 1984]

A thin lens made of glass of refractive index m = 1.5 has a focal length equal to 12 cm in air. It is now immersed in water \[\left( \mu \,=\,\frac{4}{3} \right)\]. Its new focal length is [UPSEAT 2002]

The unit of focal power of a lens is [KCET 2001]

The combination of a convex lens (f = 18 cm) and a thin concave lens (f = 9 cm) is [AMU (Engg.) 2001]

An object has image thrice of its original size when kept at 8 cm and 16 cm from a convex lens. Focal length of the lens is [UPSEAT 2001]

A convex lens has a focal length f. It is cut into two parts along the dotted line as shown in the figure. The focal length of each part will be [MP PET 2000]

Chromatic aberration of lens can be corrected by [AFMC 2000]

A lens of power + 2 diopters is placed in contact with a lens of power ? 1 diopoter. The combination will behave like [UPSEAT 2000]

A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a liquid of refractive index 1.63 is [UPSEAT 2000; Pb. PET 2004]

A lens of focal power 0.5 D is [JIPMER 1999]

A double convex lens of glass of m = 1.5 has radius of curvature of each of its surface is 0.2 m. The power of the lens is [JIPMER 1999]

A convex lens of power + 6D is placed in contact with a concave lens of power ? 4D. What is the nature and focal length of the combination [AMU (Engg.) 1999]

If a lens is cut into two pieces perpendicular to the principal axis and only one part is used, the intensity of the image [CPMT 1996]

\[{{f}_{v}}\]and \[{{f}_{r}}\] are the focal lengths of a convex lens for violet and red light respectively and \[{{F}_{v}}\] and \[{{F}_{r}}\]are the focal lengths of a concave lens for violet and red light respectively, then [CBSE PMT 1996]

If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power [CBSE PMT 1996; AFMC 2002]

A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a [IIT-JEE 1999]

A plane convex lens is made of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is [CBSE PMT 1999; Pb. PMT 1999; BHU 2001; Very Similar to BHU 2003]

A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power of a cut lens will be [MP PMT 1999]

Two lenses are placed in contact with each other and the focal length of combination is 80 cm. If the focal length of one is 20 cm, then the power of the other will be [NCERT 1981]

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of combination is [IIT-JEE 1982; AFMC 1997; CBSE PMT 2000; RPMT 2003]

A lens of power + 2 diopters is placed in contact with a lens of power - 1 diopter. The combination will behave like

A lens (focal length 50 cm) forms the image of a distant object which subtends an angle of 1 milliradian at the lens. What is the size of the image [MP PMT 1995]

In the figure, an air lens of radii of curvature 10 cm (\[{{R}_{1}}\] = \[{{R}_{2}}\] = 10 cm) is cut in a cylinder of glass\[(\mu =1.5)\]. The focal length and the nature of the lens is [MP PET 1995; Pb. PET 2000]

A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black, the image will [MP PET 1995]

A diminished image of an object is to be obtained on a screen 1.0 m from it. This can be achieved by appropriately placing [IIT JEE 1995]

If the central portion of a convex lens is wrapped in black paper as shown in the figure [Manipal MEE 1995; KCET 2001]

A plano convex lens \[(f=20cm)\]is silvered at plane surface. Now f will be [BHU 1995; DPMT 2001; MP PMT 2005]

Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact convex. The effective power of the combination is [CBSE PMT 1990; RPMT 2001]

A double convex lens of focal length 20 cm is made of glass of refractive index 3 / 2. When placed completely in water \[{{(}_{a}}{{\mu }_{w}}=4/3)\], its focal length will be [CBSE PMT 1990; MP PMT/PET 1998]

Two thin lenses, one of focal length + 60 cm and the other of focal length -20 cm are put in contact. The combined focal length is [CPMT 1973, 89; BVP 2003]

A divergent lens will produce [CPMT 1984]

A convex lens of crown glass (\[n\]=1.525) will behave as a divergent lens if immersed in [CPMT 1984]

If \[{{I}_{1}}\] and \[{{I}_{2}}\] be the size of the images respectively for the two positions of lens in the displacement method, then the size of the object is given by [CPMT 1988]

A glass lens is placed in a medium in which it is found to behave like a glass plate. Refractive index of the medium will be [CPMT 1981, 84, 85]

A thin convex lens of refractive index 1.5 has a focal length of 15 cm in air. When the lens is placed in liquid of refractive index 4/3 , its focal length will be [CPMT 1974, 77; MP PMT 1992]

The ray diagram could be correct [CPMT 1988]

A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths [IIT-JEE (Screening) 2005]

When light rays from the sun fall on a convex lens along a direction parallel to its axis [MP PMT 2004]

Two lenses of power + 12 and ? 2 diopters are placed in contact. The combined focal length of the combination will be [Pb. PET 2004]

The focal lengths of convex lens for red and blue light are 100 cm and 96.8 cm respectively. The dispersive power of material of lens is [Pb. PET 2003]

Spherical aberration in a lens [UPSEAT 2004]

A bi-convex lens made of glass (refractive index 1.5) is put in a liquid of refractive index 1.7. Its focal length will [UPSEAT 2004]

A convex lens of focal length 84 cm is in contact with a concave lens of focal length 12 cm. The power of combination (in diopters) is [MP PET 1991]

A thin convex lens of focal length 10 cm is placed in contact with a concave lens of same material and of same focal length. The focal length of combination will be [CPMT 1972; 1988]

A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen [IIT-JEE 1986; SCRA 1994; MP PET 1996; MP PMT 2004; BHU 1998, 05]

The radius of the convex surface of plano-convex lens is 20 cm and the refractive index of the material of the lens is 1.5. The focal length of the lens is [CPMT 2004]

A combination of two thin convex lenses of focal length 0.3 m and 0.1 m will have minimum spherical and chromatic aberrations if the distance between them is [UPSEE 2004]

A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is [Pb. PET 2000]