1. The disc of a siren containing 60holes rotates at a constant speed of 360rpm. The emitted sound is in unison with a tuning fork of frequency.
Correct : B. 360hz
2. The quantity which does not change, when sound enters from one medium to another
Correct : C. frequency
3. If wave y=Acos(ωt+kx) Is moving along x- axis, the shapes of a pulse at t=0 and t=2s.
Correct : B. are same
4. y1=4sin(ωt+kx), y2=-4cos(ωt+kx), the phase difference is
Correct : B. 3π/2
5. A wave equation is y=0.1sin[100πt-kx] and wave velocity is 100m/s, its number is equal to
Correct : C. π/m
6. The fundamental frequency of a sonometer wire is n. If the tension is made 3 times and length and diameter are also increased 3 times, the new frequency will be
Correct : B. n/3√3
7. Which of the following Einstein’s coefficient represents spontaneous emission?
Correct : B. a21
8. Which law is used for achieving the relation between the Einstein’s coefficients?
Correct : B. planck’s radiation law
9. The probability of spontaneous emission increases rapidly with the energy difference between the two states.
Correct : A. true
10. What is the unit for the coefficient of stimulated emission?
Correct : D. j−1 m3 s-2
11. Which Einstein’s coefficient should be used in this case?
Correct : D. b21
12. A cylindrical cavity resonator can be constructed using a circular waveguide.
Correct : A. shorted at both the ends
13. The dominant mode in the cylindrical cavity resonator is TE101 mode.
Correct : B. false
14. Circular cavities are used for microwave frequency meters.
Correct : A. true
15. The mode of the circular cavity resonator used in frequency meters is:
Correct : A. te011 mode
16. The propagation constant of TEmn mode of propagation for a cylindrical cavity resonator is:
Correct : A. 2)
17. A circular cavity resonator is filled with a dielectric of 2.08 and is operating at 5GHz of frequency. Then the wave number is:
Correct : B. 151
18. Given that the wave number of a circular cavity resonator is 151 (TE011 mode), and the length of the cavity is twice the radius of the cavity, the radius of the circular cavity operating at 5GHz frequency is:
Correct : D. insufficient data
19. A circular cavity resonator has a wave number of 151, radius of 2.74 cm, and surface resistance of 0.0184Ω. If the cavity is filled with a dielectric of 2.01, then unloaded Q due to conductor loss is:
Correct : C. 29390
20. If unloaded Q due to conductor loss and unloaded Q due to dielectric loss is 29390 and 2500 respectively, then the total unloaded Q of the circular cavity is:
Correct : C. 2300
21. The energy-level occupation for a semiconductor in thermal equilibrium is described by the
Correct : C. fermi-dirac distribution function
22. What is done to create an extrinsic semiconductor?
Correct : B. doping the material with impurities
23. The majority of the carriers in a p-type semiconductor are
Correct : A. holes
24. is used when the optical emission results from the application of electric field.
Correct : C. electro-luminescence
25. The recombination in indirect band-gap semiconductors is slow.
Correct : A. true
26. Calculate the radioactive minority carrier lifetime in gallium arsenide when the minority carriers are electrons injected into a p-type semiconductor region which has a hole concentration of 1018cm-3. The recombination coefficient for gallium arsenide is 7.21*10-10cm3s-1.
Correct : B. 1.39ns
27. Which impurity is added to gallium phosphide to make it an efficient light emitter?
Correct : C. nitrogen
28. Population inversion is obtained at a p-n junction by
Correct : D. heavy doping of both p-type and n-type material
29. A GaAs injection laser has a threshold current density of 2.5*103Acm-2 and length and width of the cavity is 240μm and 110μm respectively. Find the threshold current for the device.
Correct : B. 660 ma
30. A GaAs injection laser with an optical cavity has refractive index of 3.6. Calculate the reflectivity for normal incidence of the plane wave on the GaAs-air interface.
Correct : C. 0.32
31. A ho*mo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies.
Correct : B. false
32. How many types of hetero-junctions are available?
Correct : A. two
33. The system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region.
Correct : D. gaas/alga as dh
34. What is the principle of fibre optical communication?
Correct : C. total internal reflection
35. What is the other name for a maximum external incident angle?
Correct : D. wave guide acceptance angle
36. A single mode fibre has low intermodal dispersion than multimode.
Correct : A. true
37. How does the refractive index vary in Graded Index fibre?
Correct : B. radially
38. Which of the following has more distortion?
Correct : C. multimode step-index fibre
39. In which of the following there is no distortion?
Correct : A. graded index fibre
40. Which of the following loss occurs inside the fibre?
Correct : B. scattering
41. What causes microscopic bend?
Correct : D. non-uniform pressure
42. When more than one mode is propagating, how is it dispersed?
Correct : B. inter-modal dispersion
43. A fibre optic telephone transmission can handle more than thousands of voice channels.
Correct : A. true
44. Which of the following is known as fibre optic back bone?
Correct : D. bus topology
45. Calculate the numerical aperture of an optical fibre whose core and cladding are made of materials of refractive index 1.6 and
Correct : A. 0.55677
46. A step-index fibre has a numerical aperture of 0.26, a core refractive index of 1.5 and a core diameter of 100micrometer. Calculate the acceptance angle.
Correct : B. 15.07°
47. Multimode step index fiber has
Correct : A. large core diameter & large numerical aperture
48. 9 LOSSES ASSOCIATED WITH OPTICAL FIBERS
Correct : C. 2.6 to 50 db km-1 at wavelength 0.85μm
49. Multimode step index fiber has a large core diameter of range is
Correct : A. 100 to 300 μm
50. Multimode step index fibers have a
Correct : A. better than multimode step index fibers
51. Multimode graded index fibers with wavelength of 0.85μm have numerical aperture of 0.29 have core/cladding diameter of
Correct : B. 100 μm/140 μm
52. Multimode graded index fibers use incoherent source only.
Correct : B. false
53. In single mode fibers, which is the most beneficial index profile?
Correct : B. graded index
54. The fibers mostly not used nowadays for optical fiber communication system are
Correct : A. single mode fibers
55. Single mode fibers allow single mode propagation; the cladding diameter must be at least
Correct : D. ten times the core diameter
56. A fiber which is referred as non- dispersive shifted fiber is?
Correct : B. standard single mode fibers
57. Standard single mode fibers (SSMF) are utilized mainly for operation in
Correct : C. o-band
58. Fiber mostly suited in single-wavelength transmission in O-band is?
Correct : B. standard single mode fibers
59. Fluoride glass is used with
Correct : A. ir waves
60. Silica glass of hydroxyl concentration can be used for of wavelength.
Correct : B. 250 nm to 800 nm
61. OTDR stands for
Correct : A. optical time domain reflectometer
62. Which of the following is not correct for fibre optic sensors?
Correct : D. none of the mentioned
63. Epoxy material in fibre optics is intended for
Correct : C. better sealing
64. Plastics optical cables can be used for
Correct : A. short range
65. Which of the following represents loss associated with glass fibres?
Correct : A. 3 db/km
66. Loss associated with plastic fibre is less than glass fibres.
Correct : B. false
67. Cladding in glass fibre have high refractive index than the core.
Correct : B. false
68. The transfer of heat between two bodies in direct contact is called
Correct : C. conduction
69. In the equation, dQ=TdX
Correct : D. all of the mentioned
70. The transfer of heat between a wall and a fluid system in motion is called
Correct : B. convection
71. The specific heat of the substance is defined as the amount of heat required to raise a unit mass of the substance through a unit rise in temperature.
Correct : A. true
72. Heat and work are
Correct : D. all of the mentioned
73. Latent heat is taken at
Correct : C. both of the mentioned
74. Which of the following is true?
Correct : C. both of the mentioned
75. Heat transfer and work transfer are
Correct : D. all of the mentioned
76. A faulty thermometer has its fixed points marked as 5° and 95°. The temperature of a body as measured by the faulty thermometer is 59°. Find the correct temperature of the body on a Celsius scale.
Correct : A. 60°c
77. Temperature is a microscopic concept.
Correct : B. false
78. 2 THERMAL EXPANSION OF SOLIDS AND LIQUIDS
Correct : C. small heat capacity
79. Calorie is defined as the amount of heat required to raise the temperature of 1g of water by 1°C and it is defined under which of the following conditions?
Correct : A. from 14.5°c to 15.5°c at 760mm of hg
80. Compared to burn due to air at 100°C, a burn due to steam at 100°C is
Correct : A. more dangerous
81. 540g of ice at 0°C is mixed with 540g of water at 80°C. What is the final temperature of the mixture?
Correct : A. 0°c
82. If the sun were to increase in temperature from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on earth to what it was previously, will be
Correct : D. 64
83. On a hilly region, water boils at 95°C. What is the temperature expressed in Fahrenheit?
Correct : B. 203°f
84. Temperatures of two stars are in ratio 3:2. If wavelength of maximum intensity of first body is 4000 Å, what is corresponding wavelength of second body?
Correct : B. 6000 Å
85. Identify the given joint in Concrete Structures.
Correct : A. horizontal construction joint
86. Identify the given joint in Concrete Structures.
Correct : C. vertical construction joint
87. Identify the given type of joint in Concrete Structures.
Correct : B. t beam construction joint
88. Identify the given joint in Concrete Structures.
Correct : C. water tank joint
89. Identify the given joint in Concrete Structures.
Correct : D. dummy joint
90. For water tanks and other structure which store water, the strips of copper, aluminium, galvanized iron or other collision resistance material, known as the
Correct : B. waterstops
91. The expansion and contraction joints generally consist of some elastic material, known as which should be compressible, rigid, cellular and Resilient.
Correct : B. joint filler
92. The are provided in expansion and contraction joints to transfer the load.
Correct : A. dowels
93. The is a mixture of cement and sand, the usual proportion being 1:3.
Correct : C. gunite
94. Measurement of elevated temperatures is defined as
Correct : B. pyrometry
95. What temperature is the dark orange color associated with?
Correct : B. 1650 f
96. Bimetallic strips contain as a metal.
Correct : B. yellow brass
97. Why is invar used in bimetallic strips?
Correct : B. low coefficient of expansion
98. is commonly used in liquid- expansion thermometers.
Correct : A. bourdon tube
99. Resistance thermometer generally makes use of for the measurement of resistance.
Correct : D. wheatstone bridge
100. Which of these materials is not used for resistance coils?