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### Optics

61. Light of wavelength 550 nm falls normally on a slit of width 22 x 10-7m, the angular position of second minima from central maxima will be [2075]

14.5°

30°

42°

62°

62. Two lens of power 5D and -7.5D are placed in contact.The equivalent focal length of combination will be[2075]

-40cm

+40cm

-25cm

+25cm

63. The length of the microscope is 14 cm and magnifying power is 25 for relaxed eye the focal length of the eyepiece is 5 cm then a distance of object from objective is [2075]

2.4cm

2.1cm

1.5cm

1.8cm

63. The Illuminance at distance of 2 m from a 100 candle lamp is [2074]

10 lux

15 lux

25 lux

100 lux

64. When light beam is incident on a prism, it causes [2074]

lateral shift

dispersion only

deviation only

dispersion and deviation

65. If critical angle for a material placed in air is 30° the refractive index will be [2074]

2

0.5

1.5

2.5

67. On heating a liquid, the refractive index generally [2074]

does not change

decrease

increase

may increase or decrease depending upon the rate of heating

61. The field of view is maximum for. [2073]

plane mirror

concave mirror

convex spectrum

Cylindrical mirror

62. The sky seen from earth appears blue because of [2073]

scattering of lights

dispersion of lights

reflection

polarization

63. A person cannot see objects clearly beyond 50 cm. The power of the lens to correct the vision is [2073]

+5D

-5 D

-0.5 D

-2 D

61. A ray of light in air enters a glass slab. Its [2072]

wave length decrease

wave length increases

speed increases

frequency decreases

62. By using white light in double slit interference experiment the central fringe is white. What color of fringe can be seen nearest to the central fringe? [2072]

blue

green

red

violet

63. A convex lens is immersed in water. Compared to its power in air, the power in water will [2072]

increase for red and decrease for blue

decrease for all colors

be same for all colors

increase for all colors

63. The image of an object placed at the focus of conves mirror is ar a distance [2071]

f

2f

f/2

64. If sky is seen from moon's surface, it will appear [2071]

black

Blue

White

Red

65. A double convex air bubble in a glass sheet would behave as a [2071]

Convergent lengs

Concave mirror

Divergent Lens

Plane Mirror

66. When two prism are combined it gives [2071]

Reflection only

lateral shift

Dispersion and deviation both

Dispersion or deviation

59. The image of an object placed at the focus of a concave mirror is at

f

Infinity

2f

f/2

61. The refractive index of air with respect to glass is 2/3. The refractive index of diamond with respect to air is 12/5. Then the refractive index of glass with respect to diamond will be. [2070]

5/8

8/9

5/18

18/5

62. The focal length of a double conves lens for which radius of curvature of each surface is R will be ....( µ = 1.5) [2070]

R/2

R

2R

4R

63. Light of wave length 7200 Å in air has wave length in glass equal to ......... (given Refractive index of glass with respect to air = 1.5) [2070]

7200 Å

4800 Å

1080 Å

10800 Å

58. A myopic eye cannot see object beyond 1.5m. What power of lens will be required to correct this defect of vision? [2069]

1.5 D

0.66 D

-1.5 D

-0.66 D

59. The critical angel of glass water interface is [2069]

sin-1(8/9)

sin-1(4/5)

sin-1(3/4)

sin-1(2/3)

60. A Diffraction granting has 5000 lines per cm. The maximum order visible with the radiation of wavelength 600 nm in diffraction experiment. [2069]

2

3

4

0

61. Light travels through a glass of thickness t and refractive index n. If C is the velocity of light in vacuum, the time taken by light to travel this thickness is[2069]

t/ne

cnt

nt/c

tc/n

I there is