12583 + Mcqs in Physics Page 236 McqOptions

11751.	A plano-convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object [AIEEE 2004]
A.	20 cm
B.	30 cm
C.	60 cm
D.	80 cm
Answer» B. 30 cm

Discussion

11752.	In order to obtain a real image of magnification 2 using a converging lens of focal length 20 cm, where should an object be placed [AFMC 2004]
A.	50 cm
B.	30 cm
C.	? 50 cm
D.	? 30 cm
Answer» E.

Discussion

11753.	A thin plano-convex lens acts like a concave mirror of focal length 0.2 m when silvered from its plane surface. The refractive index of the material of the lens is 1.5. The radius of curvature of the convex surface of the lens will be [KCET 2004]
A.	0.4 m
B.	0.2 m
C.	0.1 m
D.	0.75 m
Answer» C. 0.1 m

Discussion

11754.	A point object is placed at the center of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is [IIT-JEE (Screening) 2004]
A.	2 cm
B.	4 cm
C.	6 cm
D.	12 cm
Answer» D. 12 cm

Discussion

11755.	A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is [KCET 2004]
A.	The focal point shifts away from the lens by a small distance
B.	The focus remains undisturbed
C.	The focus shifts to infinity
D.	The focal point shifts towards the lens by a small distance
Answer» D. The focal point shifts towards the lens by a small distance

Discussion

11756.	In a parallel beam of white light is incident on a converging lens, the colour which is brought to focus nearest to the lens is [JIPMER 1999]
A.	Violet
B.	Red
C.	The mean colour
D.	All the colours together
Answer» B. Red

Discussion

11757.	An object placed 10 cm in front of a lens has an image 20 cm behind the lens. What is the power of the lens (in dioptres) [MP PMT 1995]
A.	1.5
B.	3
C.	? 15.0
D.	15
Answer» E.

Discussion

11758.	An achromatic combination of lenses produces [KCET 1993; JIPMER 1997]
A.	Coloured images
B.	Highly enlarged image
C.	Images in black and white
D.	Images unaffected by variation of refractive index with wavelength
Answer» E.

Discussion

11759.	When the convergent nature of a convex lens will be less as compared with air [AFMC 2003]
A.	In water
B.	In oil
C.	In both (a) and (b)
D.	None of these
Answer» D. None of these

Discussion

11760.	Two thin lenses of focal lengths f1 and f2 are in contact. The focal length of this combination is [MP PET 2002]
A.	\[\frac{{{f}_{1}}{{f}_{2}}}{{{f}_{1}}-{{f}_{2}}}\]
B.	\[\frac{{{f}_{1}}{{f}_{2}}}{{{f}_{1}}+{{f}_{2}}}\]
C.	\[\frac{2{{f}_{1}}{{f}_{2}}}{{{f}_{1}}-{{f}_{2}}}\]
D.	\[\frac{2{{f}_{1}}{{f}_{2}}}{{{f}_{1}}+{{f}_{2}}}\]
Answer» C. \[\frac{2{{f}_{1}}{{f}_{2}}}{{{f}_{1}}-{{f}_{2}}}\]

Discussion

11761.	The focal length of lens of refractive index 1.5 in air is 30 cm. When it is immersed in a liquid of refractive index \[\frac{4}{3}\], then its focal length in liquid will be [BHU 2002]
A.	30 cm
B.	60 cm
C.	120 cm
D.	240 cm
Answer» D. 240 cm

Discussion

11762.	A point object O is placed in front of a glass rod having spherical end of radius of curvature 30 cm. The image would be formed at [Orissa JEE 2002]
A.	30 cm left
B.	Infinity
C.	1 cm to the right
D.	18 cm to the left
Answer» B. Infinity

Discussion

11763.	A convex lens is made up of three different materials as shown in the figure. For a point object placed on its axis, the number of images formed are [KCET 2002]
A.	1
B.	5
C.	4
D.	3
Answer» E.

Discussion

11764.	A convex lens produces a real image m times the size of the object. What will be the distance of the object from the lens [JIPMER 2002]
A.	\[\left( \frac{m+1}{m} \right)f\]
B.	(m ?1)f
C.	\[\left( \frac{m-1}{m} \right)f\]
D.	\[\frac{m+1}{f}\]
Answer» B. (m ?1)f

Discussion

11765.	If two + 5 D lenses are mounted at some distance apart, the equivalent power will always be negative if the distance is [UPSEAT 2002]
A.	Greater than 40 cm
B.	Equal to 40 cm
C.	Equal to 10 cm
D.	Less than 10 cm
Answer» B. Equal to 40 cm

Discussion

11766.	A light bulb is placed between two plane mirrors inclined at an angle of \[60{}^\circ .\] The number of images formed are [NCERT 1980; CPMT 1996, 97; SCRA 1994; AIIMS 1997; RPMT 1999; AIEEE 2002; Orissa JEE 2003; MP PMT 2004; MP PET 2004]
A.	6
B.	2
C.	5
D.	4
Answer» D. 4

Discussion

11767.	It is desired to photograph the image of an object placed at a distance of \[3m\] from the plane mirror. The camera which is at a distance of \[4.5m\] from the mirror should be focussed for a distance of [NCERT 1971]
A.	\[3m\]
B.	\[4.5m\]
C.	\[6m\]
D.	\[7.5m\]
Answer» E.

Discussion

11768.	A plane mirror is approaching you at a speed of \[10\,cm/sec\]You can see your image in it. At what speed will your image approach you [CPMT 1974]
A.	\[10cm/sec\]
B.	\[5cm/sec\]
C.	\[20cm/sec\]
D.	\[15cm/sec\]
Answer» D. \[15cm/sec\]

Discussion

11769.	Focal length of a plane mirror is [RPMT 2000]
A.	Zero
B.	Infinite
C.	Very less
D.	Indefinite
Answer» C. Very less

Discussion

11770.	A light beam is being reflected by using two mirrors, as in a periscope used in submarines. If one of the mirrors rotates by an angle q, the reflected light will deviate from its original path by the angle [UPSEAT 2004]
A.	\[2\theta \]
B.	\[{{0}^{o}}\]
C.	\[\theta \]
D.	\[4\theta \]
Answer» B. \[{{0}^{o}}\]

Discussion

11771.	A plane mirror reflects a pencil of light to form a real image. Then the pencil of light incident on the mirror is [MP PMT 1997; DCE 2001, 03]
A.	Parallel
B.	Convergent
C.	Divergent
D.	None of the above
Answer» C. Divergent

Discussion

11772.	A man having height 6 m. He observes image of 2 m height erect, then mirror used is [BCECE 2004]
A.	Concave
B.	Convex
C.	Plane
D.	None of these
Answer» C. Plane

Discussion

11773.	Two vertical plane mirrors are inclined at an angle of \[60{}^\circ \] with each other. A ray of light travelling horizontally is reflected first from one mirror and then from the other. The resultant deviation is
A.	\[60{}^\circ \]
B.	\[120{}^\circ \]
C.	\[180{}^\circ \]
D.	\[240{}^\circ \]
Answer» E.

Discussion

11774.	If the luminous intensity of a 100 W unidirectional bulb is 100 candela, then total luminous flux emitted from the bulb is [AIIMS 1998]
A.	861 lumen
B.	986 lumen
C.	1256 lumen
D.	1561 lumen
Answer» D. 1561 lumen

Discussion

11775.	Total flux produced by a source of 1 cd is [CPMT 2001]
A.	\[\frac{1}{4\pi }\]
B.	\[8\pi \]
C.	\[4\pi \]
D.	\[\frac{1}{8\pi }\]
Answer» D. \[\frac{1}{8\pi }\]

Discussion

11776.	"Lux" is a unit of [Kerala PMT 2001]
A.	Luminous intensity of a source
B.	Illuminance on a surface
C.	Transmission coefficient of a surface
D.	Luminous efficiency of source of light
Answer» C. Transmission coefficient of a surface

Discussion

11777.	Find the luminous intensity of the sun if it produces the same illuminance on the earth as produced by a bulb of 10000 candela at a distance 0.3 m. The distance between the sun and the earth is \[1.5\times {{10}^{11}}m\]
A.	\[25\times {{10}^{22}}cd\]
B.	\[25\times {{10}^{18}}cd\]
C.	\[25\times {{10}^{26}}cd\]
D.	\[25\times {{10}^{36}}cd\]
Answer» D. \[25\times {{10}^{36}}cd\]

Discussion

11778.	The relative luminosity of wavelength 600 nm is 0.6. Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555 nm
A.	50W
B.	72W
C.	\[120\times {{(0.6)}^{2}}W\]
D.	200W
Answer» E.

Discussion

11779.	Figure shows a glowing mercury tube. The illuminances at point A, B and C are related as
A.	B > C > A
B.	A > C > B
C.	B = C > A
D.	B = C < A
Answer» E.

Discussion

11780.	A point source of 3000 lumen is located at the centre of a cube of side length 2m. The flux through one side is
A.	500 lumen
B.	600 lumen
C.	750 lumen
D.	1500 lumen
Answer» B. 600 lumen

Discussion

11781.	A screen receives 3 watt of radiant flux of wavelength 6000 Å. One lumen is equivalent to \[1.5\times {{10}^{-3}}watt\] of monochromatic light of wavelength 5550 Å. If relative luminosity for 6000 Å is 0.685 while that for 5550 Å is 1.00, then the luminous flux of the source is
A.	\[4\times {{10}^{3}}lm\]
B.	\[3\times {{10}^{3}}lm\]
C.	\[2\times {{10}^{3}}lm\]
D.	\[1.37\times {{10}^{3}}lm\]
Answer» E.

Discussion

11782.	In the above problem, the luminous flux emitted by sun will be
A.	\[4.43\times {{10}^{25}}\ lm\]
B.	\[4.43\times {{10}^{26}}\ lm\]
C.	\[4.43\times {{10}^{27}}\ lm\]
D.	\[4.43\times {{10}^{28}}\ lm\]
Answer» E.

Discussion

11783.	A lamp is hanging along the axis of a circular table of radius r. At what height should the lamp be placed above the table, so that the illuminance at the edge of the table is \[\frac{1}{8}\] of that at its center [MP PET 2005]
A.	\[\frac{r}{2}\]
B.	\[\frac{r}{\sqrt{2}}\]
C.	\[\frac{r}{3}\]
D.	\[\frac{r}{\sqrt{3}}\]
Answer» E.

Discussion

11784.	Two lamps of luminous intensity of 8 Cd and 32 Cd respectively are lying at a distance of 1.2 m from each other. Where should a screen be placed between two lamps such that its two faces are equally illuminated due to two sources
A.	10 cm from 8 Cd lamp
B.	10 cm from 32Cd lamp
C.	40 cm from 8 Cd lamp
D.	40 cm from 32 Cd lamp
Answer» D. 40 cm from 32 Cd lamp

Discussion

11785.	Two light sources with equal luminous intensity are lying at a distance of 1.2 m from each other. Where should a screen be placed between them such that illuminance on one of its faces is four times that on another face
A.	0.2 m
B.	0.4 m
C.	0.8 m
D.	1.6 m
Answer» D. 1.6 m

Discussion

11786.	The intensity of direct sunlight on a surface normal to the rays is \[{{I}_{0}}\]. What is the intensity of direct sunlight on a surface, whose normal makes an angle of 60o with the rays of the sun [CPMT 1981]
A.	\[{{I}_{0}}\]
B.	\[{{I}_{0}}\left( \frac{\sqrt{3}}{2} \right)\]
C.	\[\frac{{{I}_{0}}}{2}\]
D.	\[2{{I}_{0}}\]
Answer» D. \[2{{I}_{0}}\]

Discussion

11787.	Two stars situated at distances of 1 and 10 light years respectively from the earth appear to possess the same brightness. The ratio of their real brightness is [NCERT 1981]
A.	1 : 10
B.	10 : 1
C.	1 : 100
D.	100 : 1
Answer» D. 100 : 1

Discussion

11788.	A lamp is hanging 1 m above the centre of a circular table of diameter 1m. The ratio of illuminaces at the centre and the edge is [NCERT 1982]
A.	\[\frac{1}{2}\]
B.	\[{{\left( \frac{5}{4} \right)}^{\frac{3}{2}}}\]
C.	\[\frac{4}{3}\]
D.	\[\frac{4}{5}\]
Answer» C. \[\frac{4}{3}\]

Discussion

11789.	To prepare a print the time taken is 5 sec due to lamp of 60 watt at 0.25 m distance. If the distance is increased to 40 cm then what is the time taken to prepare the similar print [CPMT 1982]
A.	3.1 sec
B.	1 sec
C.	12.8 sec
D.	16 sec
Answer» D. 16 sec

Discussion

11790.	Venus looks brighter than other stars because [MNR 1985]
A.	It has higher density than other stars
B.	It is closer to the earth than other stars
C.	It has no atmosphere
D.	Atomic fission takes place on its surface
Answer» C. It has no atmosphere

Discussion

11791.	A source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as [CPMT 1986]
A.	Luminous energy emitted by the source per second
B.	Luminous flux emitted by source per unit solid angle
C.	Luminous flux falling per unit area of a given surface
D.	Luminous flux coming per unit area of an illuminated surface
Answer» C. Luminous flux falling per unit area of a given surface

Discussion

11792.	Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is [CPMT 1992]
A.	80 W
B.	176 W
C.	88 W
D.	36 W
Answer» D. 36 W

Discussion

11793.	Lux is equal to [CPMT 1993]
A.	1 lumen/m2
B.	1 lumen/cm2
C.	1 candela/m2
D.	1 candela/cm2
Answer» D. 1 candela/cm2

Discussion

11794.	A small lamp is hung at a height of 8 feet above the centre of a round table of diameter 16 feet. The ratio of intensities of illumination at the centre and at points on the circumference of the table will be [CPMT 1984, 1996]
A.	1 : 1
B.	2 : 1
C.	\[2\sqrt{2}:1\]
D.	3 : 2
Answer» D. 3 : 2

Discussion

11795.	A fish is vertically below a flying bird moving vertically= down towards water surface. The bird will appear to the fish to be
A.	Moving faster than its speed and also away from the real distance
B.	Moving faster than its real speed and nearer than its real distance
C.	Moving slower than its real speed and also nearer than its real distance
D.	Moving slower than its real speed and away from the real distance
Answer» B. Moving faster than its real speed and nearer than its real distance

Discussion

11796.	Consider an equiconvex lens of radius of curvature R and focal length\[f.\,\]If \[f>R\,\], the refractive index \[\mu \]of the material of the lens
A.	Is greater than zero but less than 1.5
B.	Is greater than 1.5 but less than 2.0
C.	Is greater than 1.0 but less than 1.5
D.	None of these
Answer» D. None of these

Discussion

11797.	A concave mirror is placed at the bottom of an empty tank with face upwards and axis vertical. When sunlight falls normally on the mirror, it is focussed at distance of 32 cm from the mirror. If the tank filled with Water \[\left( \mu =\frac{4}{3} \right)\] up to a height of 20 cm, then the sunlight will now get focused at
A.	16 cm above water level
B.	9 cm above water level
C.	24 cm below water level
D.	9 cm below water level
Answer» C. 24 cm below water level

Discussion

11798.	The resolving power of a telescope depends on [MP PET 2000, 01; DCE 2003]
A.	Focal length of eye lens
B.	Focal length of objective lens
C.	Length of the telescope
D.	Diameter of the objective lens
Answer» E.

Discussion

11799.	In a terrestrial telescope, the focal length of objective is 90 cm, of inverting lens is \[5\,cm\]and of eye lens is \[6\,cm.\]If the final image is at 30 cm, then the magnification will be [DPMT 2001]
A.	21
B.	12
C.	18
D.	15
Answer» D. 15

Discussion

11800.	The sun's diameter is \[1.4\times {{10}^{9}}m\] and its distance from the earth is \[{{10}^{11}}m.\] The diameter of its image, formed by a convex lens of focal length \[2\,m\]will be [MP PET 2000]
A.	0.7 cm
B.	1.4 cm
C.	2.8 cm
D.	Zero (i.e. point image)
Answer» D. Zero (i.e. point image)

Discussion

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

A plano-convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object [AIEEE 2004]

In order to obtain a real image of magnification 2 using a converging lens of focal length 20 cm, where should an object be placed [AFMC 2004]

A thin plano-convex lens acts like a concave mirror of focal length 0.2 m when silvered from its plane surface. The refractive index of the material of the lens is 1.5. The radius of curvature of the convex surface of the lens will be [KCET 2004]

A point object is placed at the center of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is [IIT-JEE (Screening) 2004]

A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is [KCET 2004]

In a parallel beam of white light is incident on a converging lens, the colour which is brought to focus nearest to the lens is [JIPMER 1999]

An object placed 10 cm in front of a lens has an image 20 cm behind the lens. What is the power of the lens (in dioptres) [MP PMT 1995]

An achromatic combination of lenses produces [KCET 1993; JIPMER 1997]

When the convergent nature of a convex lens will be less as compared with air [AFMC 2003]

Two thin lenses of focal lengths f1 and f2 are in contact. The focal length of this combination is [MP PET 2002]

The focal length of lens of refractive index 1.5 in air is 30 cm. When it is immersed in a liquid of refractive index \[\frac{4}{3}\], then its focal length in liquid will be [BHU 2002]

A point object O is placed in front of a glass rod having spherical end of radius of curvature 30 cm. The image would be formed at [Orissa JEE 2002]

A convex lens is made up of three different materials as shown in the figure. For a point object placed on its axis, the number of images formed are [KCET 2002]

A convex lens produces a real image m times the size of the object. What will be the distance of the object from the lens [JIPMER 2002]

If two + 5 D lenses are mounted at some distance apart, the equivalent power will always be negative if the distance is [UPSEAT 2002]

A light bulb is placed between two plane mirrors inclined at an angle of \[60{}^\circ .\] The number of images formed are [NCERT 1980; CPMT 1996, 97; SCRA 1994; AIIMS 1997; RPMT 1999; AIEEE 2002; Orissa JEE 2003; MP PMT 2004; MP PET 2004]

It is desired to photograph the image of an object placed at a distance of \[3m\] from the plane mirror. The camera which is at a distance of \[4.5m\] from the mirror should be focussed for a distance of [NCERT 1971]

A plane mirror is approaching you at a speed of \[10\,cm/sec\]You can see your image in it. At what speed will your image approach you [CPMT 1974]

Focal length of a plane mirror is [RPMT 2000]

A light beam is being reflected by using two mirrors, as in a periscope used in submarines. If one of the mirrors rotates by an angle q, the reflected light will deviate from its original path by the angle [UPSEAT 2004]

A plane mirror reflects a pencil of light to form a real image. Then the pencil of light incident on the mirror is [MP PMT 1997; DCE 2001, 03]

A man having height 6 m. He observes image of 2 m height erect, then mirror used is [BCECE 2004]

Two vertical plane mirrors are inclined at an angle of \[60{}^\circ \] with each other. A ray of light travelling horizontally is reflected first from one mirror and then from the other. The resultant deviation is

If the luminous intensity of a 100 W unidirectional bulb is 100 candela, then total luminous flux emitted from the bulb is [AIIMS 1998]

Total flux produced by a source of 1 cd is [CPMT 2001]

"Lux" is a unit of [Kerala PMT 2001]

Find the luminous intensity of the sun if it produces the same illuminance on the earth as produced by a bulb of 10000 candela at a distance 0.3 m. The distance between the sun and the earth is \[1.5\times {{10}^{11}}m\]

The relative luminosity of wavelength 600 nm is 0.6. Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555 nm

Figure shows a glowing mercury tube. The illuminances at point A, B and C are related as

A point source of 3000 lumen is located at the centre of a cube of side length 2m. The flux through one side is

A screen receives 3 watt of radiant flux of wavelength 6000 Å. One lumen is equivalent to \[1.5\times {{10}^{-3}}watt\] of monochromatic light of wavelength 5550 Å. If relative luminosity for 6000 Å is 0.685 while that for 5550 Å is 1.00, then the luminous flux of the source is

In the above problem, the luminous flux emitted by sun will be

A lamp is hanging along the axis of a circular table of radius r. At what height should the lamp be placed above the table, so that the illuminance at the edge of the table is \[\frac{1}{8}\] of that at its center [MP PET 2005]

Two lamps of luminous intensity of 8 Cd and 32 Cd respectively are lying at a distance of 1.2 m from each other. Where should a screen be placed between two lamps such that its two faces are equally illuminated due to two sources

Two light sources with equal luminous intensity are lying at a distance of 1.2 m from each other. Where should a screen be placed between them such that illuminance on one of its faces is four times that on another face

The intensity of direct sunlight on a surface normal to the rays is \[{{I}_{0}}\]. What is the intensity of direct sunlight on a surface, whose normal makes an angle of 60o with the rays of the sun [CPMT 1981]

Two stars situated at distances of 1 and 10 light years respectively from the earth appear to possess the same brightness. The ratio of their real brightness is [NCERT 1981]

A lamp is hanging 1 m above the centre of a circular table of diameter 1m. The ratio of illuminaces at the centre and the edge is [NCERT 1982]

To prepare a print the time taken is 5 sec due to lamp of 60 watt at 0.25 m distance. If the distance is increased to 40 cm then what is the time taken to prepare the similar print [CPMT 1982]

Venus looks brighter than other stars because [MNR 1985]

A source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as [CPMT 1986]

Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is [CPMT 1992]

Lux is equal to [CPMT 1993]

A small lamp is hung at a height of 8 feet above the centre of a round table of diameter 16 feet. The ratio of intensities of illumination at the centre and at points on the circumference of the table will be [CPMT 1984, 1996]

A fish is vertically below a flying bird moving vertically= down towards water surface. The bird will appear to the fish to be

Consider an equiconvex lens of radius of curvature R and focal length\[f.\,\]If \[f>R\,\], the refractive index \[\mu \]of the material of the lens

The resolving power of a telescope depends on [MP PET 2000, 01; DCE 2003]

In a terrestrial telescope, the focal length of objective is 90 cm, of inverting lens is \[5\,cm\]and of eye lens is \[6\,cm.\]If the final image is at 30 cm, then the magnification will be [DPMT 2001]

The sun's diameter is \[1.4\times {{10}^{9}}m\] and its distance from the earth is \[{{10}^{11}}m.\] The diameter of its image, formed by a convex lens of focal length \[2\,m\]will be [MP PET 2000]