JEE Questions for Physics Ray Optics Quiz 19 - MCQExams.com

A 60 watt bulb is hung over the center of a table 4 m × 4 m at a height of 3 m. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is
  • (17/13)3/2
  • 2/1
  • 17/13
  • 5/4
If the luminous intensity of a 100 W unidirectional bulb is 100 candela, then total luminous flux emitted from the bulb is
  • 861 lumen
  • 986 lumen
  • 1256 lumen
  • 1561 lumen
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
  • 1 : 1
  • 2 : 1

  • Physics-Ray Optics-86339.png
  • 3 : 2
Lux is equal to
  • 1 lumen/m2
  • 1 lumen/cm2
  • 1 candela/m2
  • 1 candela/cm2
Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is
  • 36 W
  • 80 W
  • 176 W
  • 88 W
A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is
  • 1/3
  • 16/27
  • 1/4
  • 1/9
The distance between a point source of light and a screen which is 60 cm is increased to 180 cm. The intensity on the screen as compared with the original intensity will be
  • (1/times
  • (1/times
  • 3 times
  • 9 times
A source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as
  • Luminous energy emitted by the source per second
  • Luminous flux emitted by source per unit solid angle
  • Luminous flux falling per unit area of a given surface
  • Luminous flux coming per unit area of an illuminated surface
Venus looks brighter than other stars because
  • It has higher density than other stars
  • It is closer to the earth than other stars
  • It has no atmosphere
  • Atomic fission takes place on its surface
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
  • 3.1 s
  • 1 s
  • 12.8 s
  • 16 s
A lamp is hanging lm above the centre of a circular table of diameter lm. The ratio of illuminaces at the centre and the edge is

  • Physics-Ray Optics-86347.png
  • 2)
    Physics-Ray Optics-86348.png

  • Physics-Ray Optics-86349.png

  • Physics-Ray Optics-86350.png
A lamp is hanging at a height of 4m above a table. The lamp is lowered by lm. The percentage increase in illuminace will be
  • 40%
  • 64%
  • 78%
  • 92%
The intensity of direct sunlight on a surface normal to the rays is I0. What is the intensity of direct sunlight on a surface, whose normal makes an angle of 60° with the rays of the sun

  • Physics-Ray Optics-86353.png
  • 2)
    Physics-Ray Optics-86354.png

  • Physics-Ray Optics-86355.png

  • Physics-Ray Optics-86356.png
Inverse square law for illuminance is valid for
  • Isotropic point source
  • Cylindrical source
  • Search light
  • All types of sources
1% of light of a source with luminous intensity 50 candela is incident on a circular surface of radius 10 cm. The average illuminance of surface is
  • 100 lux
  • 200 lux
  • 300 lux
  • 400 lux
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
  • 0.2 m
  • 0.4 m
  • 0.8 m
  • 1.6 m
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
  • 10 cm from 8 Cd lamp
  • 10 cm from 32 Cd lamp
  • 40 cm from 8 Cd lamp
  • 40 cm from 32 Cd lamp
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 ofthe table is 1/8 of that at its center

  • Physics-Ray Optics-86361.png
  • 2)
    Physics-Ray Optics-86362.png

  • Physics-Ray Optics-86363.png

  • Physics-Ray Optics-86364.png
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 × 1011 m
  • 25 × 1022 cd
  • 25 × 1018 cd
  • 25 × 1026 cd
  • 25 × 1036 cd
A lamp is hanging at a height 40 cm from the centre of a table. If its height is increased by 10 cm the illuminance on the table will decrease by
  • 10%
  • 20%
  • 27%
  • 36%
Which has more luminous efficiency?
  • A 40 W bulb
  • A 40 W fluorescent tube
  • Both have same
  • Cannot say
An electric lamp is fixed at the ceiling of a circular tunnel as shown is figure. What is the ratio the intensities of light at base A and a point B on the wall
Physics-Ray Optics-86368.png
  • 1 : 2
  • 2)
    Physics-Ray Optics-86369.png

  • Physics-Ray Optics-86370.png

  • Physics-Ray Optics-86371.png
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
  • 50 W
  • 72 W
  • 120 × (0.6)2 W
  • 200 W
Figure shows a glowing mercury tube. The illuminances at point A, B and C are related as
Physics-Ray Optics-86374.png
  • B > C > A
  • A > C > B
  • B = C > A
  • B = C < A
A screen receives 3 watt of radiant flux of wavelength 6000 Å. One lumen is equivalent to 1.5 × 10–3watt 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
  • 4 × 103 lm
  • 3 × 1031m
  • 2 × 103 lm
  • 1.37 × 103 lm
A point source of 3000 lumen is located at the centre of a cube of side length 2m. The flux through one side is
  • 500 lumen
  • 600 lumen
  • 750 lumen
  • 1500 lumen
A point source of light moves in a straight line parallel to a plane table. Consider a small portion of the table directly below the line of movement of the source. The illuminance at this portion varies with its distance r from the source as

  • Physics-Ray Optics-86377.png
  • 2)
    Physics-Ray Optics-86378.png

  • Physics-Ray Optics-86379.png

  • Physics-Ray Optics-86380.png
A point source of light Bis placed at a distance Lin front of the centre of a mirror of width dhung vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is
Physics-Ray Optics-86382.png
  • d/2
  • d
  • 2 d
  • 3 d
Two plane mirrors A and B are aligned parallel to each other, as shown in the figure. A light ray is incident at an angle of 30° at a point just inside one end of A. The plane of incidence coincides with the plane of the figure. The maximum number of times the ray undergoes reflections (including the first one) before itemerges out is
Physics-Ray Optics-86384.png
  • 28
  • 30
  • 32
  • 34
A concave mirror of focal length 100cm is used to obtain the image of the sun which subtends an angle of 30\'. The diameter of the image of the sun will be
  • 1.74 cm
  • 0.87 cm
  • 0.435 cm
  • 100 cm
A square of side 3 cm is placed at a distance of 25 cm from a concave mirror of focal length 10cm. The centre of the square is at the axis of the mirror and the plane is normal to the axis. The area enclosed by the image of the square is
  • 4 cm2
  • 6 cm2
  • 16 cm2
  • 36 cm2
A thin rod of lengthf/3 lies along the axis of a concave mirror of focal length f. One end of its magnified image touches an end of the rod. The length of the image is

  • Physics-Ray Optics-86388.png
  • 2)
    Physics-Ray Optics-86389.png

  • Physics-Ray Optics-86390.png

  • Physics-Ray Optics-86391.png
A ray of light falls on the surface of a spherical glass paper weight making an angle α with the normal and is refracted in the medium at an angle β. The angle of deviation of the emergent ray from the direction of the incident ray
  • (α – β)
  • 2 (α – β)
  • (α – β) / 2
  • (β – α)
The light reflected by a plane mirror may form a real image
  • If the rays incident on the mirror are diverging
  • If the rays incident on the mirror are converging
  • If the object is placed very close to the mirror
  • Under no circumstances
A glass hemisphere of radius 0.04 m and R.I. of the material 1.6 is placed centrally over a cross mark on a paper (i) with the flat face; (ii) with the curved face in contact with the paper. In each case the cross mark is viewed directly from above. The position of the images will be
  • (i) 0.04 m from the flat face; (ii) 0.025 m from the flat face
  • (i) At the same position of the cross mark; (ii) 0.025 m below the flat face
  • (i) 0.025 m from the flat face; (ii) 0.04 m from the flat face
  • For both (i) and (ii) 0.025 m from the highest point of the hemisphere
One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is
  • 0.4
  • 0.8
  • 1.2
  • 1.6
A rectangular glass slab ABCD, of refractive index n1, is immersed in water of refractive index n2 (n1< n2). A ray of light in incident at the surface AB of the slab as shown. The maximum value of the angle of incidence αmax, such that the ray comes out only from the other surface CD is given by
Physics-Ray Optics-86396.png

  • Physics-Ray Optics-86397.png
  • 2)
    Physics-Ray Optics-86398.png

  • Physics-Ray Optics-86399.png

  • Physics-Ray Optics-86400.png
A diverging beam of light from a point source S having divergence angle α, falls symmetrically on a glass slab as shown. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and the refractive index n, then the divergence angle of theemergent beam is
Physics-Ray Optics-86402.png
  • Zero
  • α
  • sin–1 (1/n)
  • 2 sin–1 (1/n)

Physics-Ray Optics-86404.png
  • 16 cm above water level
  • 9 cm above water level
  • 24 cm below water level
  • 9 cm below water level
An observer can see through a pin-hole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then, the refractive index of theliquid is
Physics-Ray Optics-86406.png

  • Physics-Ray Optics-86407.png
  • 2)
    Physics-Ray Optics-86408.png

  • Physics-Ray Optics-86409.png

  • Physics-Ray Optics-86410.png
A ray of light is incident at the glass-water interface at an angle i, it emerges finally parallel to the surface of water, then the value of μgwould be
Physics-Ray Optics-86412.png
  • (4/3)sin i
  • 1/sin i
  • 4/3
  • 1
A glass prism (μ = 1.is dipped in water (μ = 4/as shown in figure. A light ray is incident normally on the surface AB. It reaches the surface BC after totally reflected, if
Physics-Ray Optics-86414.png
  • sin θ ≥ 8/ 9
  • 2/3 < sin θ < 8/9
  • sin θ ≤ 2/3
  • It is not possible
A convex lens A of focal length 20 cm and a concave lens B of focal length 5 cm are kept along the same axis with the distance dbetween them. If a parallel beam of light falling on A leaves B as a parallel beam, then distance d in cm will be
  • 25
  • 15
  • 30
  • 50
Diameter of a plano-convex lens is 6 cm and thickness at the centre is 3 mm. If the speed of light in the maternal of the lens is 2 × 108 m/s, the focal length ofthe lens is
  • 15 cm
  • 20 cm
  • 30 cm
  • 10 cm
A point object Ois placed on the principal axis of a convex lens of focal length 20 cm at a distance of 40 cm to the left of it. The diameter of the lens is 10 cm. If the eye is placed 60 cm to the right of the lens at a distance hbelow the principal axis, then the maximum value of hto see the image will be
  • 0
  • 5 cm
  • 2.5 cm
  • 10 cm
A hollow double concave lens is made of very thin transparent material. It can be filled with air or either of two liquids L1 and L2having refractive indices n1 and n2 respectively (n2> n1> 1). The lens will diverge a parallel beam of light if it is filled with
  • Air and placed in air
  • Air and immersed in L1
  • L1 and immersed in L2
  • L2and immersed in L1
A biconvex lens of focal length 15 cm is in front of a plane mirror. The distance between the lens and the mirror is 10 cm. A small object is kept at a distance of30 cm from the lens. The final image is
  • Virtual and at a distance of 16 cm from mirror
  • Real and at distance of 16 cm from the mirror
  • Virtual and at a distance of 20 cm from the mirror
  • Real and at a distance of 20 cm from the mirror
Which one of the following spherical lenses does not exhibit dispersion? The radii of curvature of thesurfaces of the lenses are as given in the diagrams

  • Physics-Ray Optics-86421.png
  • 2)
    Physics-Ray Optics-86422.png

  • Physics-Ray Optics-86423.png

  • Physics-Ray Optics-86424.png
The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size ofthe image
  • 1.25 cm
  • 2.5 cm
  • 1.05 cm
  • 2 cm
An achromatic prism is made by crown glass prism(Ac = 19°) and flint glass prism (Af = 6°).If Cμv= 1.5 and Fμv = 1.66, then resultant deviation forred coloured ray will be
  • 1.04°
  • 5°
  • 0.96°
  • 13.5°
0:0:1


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