MCQ of Illumination
1. Radiant efficiency of the luminous source depends on(A) shape of the source
(B) temperature of the source
(C) wavelength of light rays
(D) all of the above.
2. Light waves travel with a velocity of
(A) 3 x 1010cm/s
(B) 3 x 1012cm/s
(C) 3 x 1015 cm/s
(D) 3 x 1018 cm/s
3. Carbon arc lamps are commonly used in
(A) domestic lighting
(B) street lighting
(C) cinema projectors
(D) photography.
4. The unit of solid angle is
(A) solid angle
(B) radian
(C) steradian
(D) candela.
5. Candela is the unit of
(A) Luminous flux
(B) Luminous intensity
(C) Wavelength
(D) None of the above.
6. The unit of luminous flux is
(A) steradian
(B) candela
(C) lumen
(D) lux.
7. The illumination is directly proportional to the cosine of the angle made by the normal to the illuminated surface with the direction of the incident flux. Above statement is associated with
(A) Planck's law
(B) Macbeth's law of illumination
(C) Bunsen's law of illumination
(D) Lambert's cosine law.
8. Illumination level required for precision work is around
(A) 50 lm/m2
(B) 100 lm/m2
(C) 200 lm/m2
(D) 500 lm/m2.
9. Which of the following will need the highest level of illumination ?
(A) Proof reading
(B) Bed rooms
(C) Hospital wards
(D) Railway platforms.
10. Which of the following will need lowest level of illumination ?
(A) Displays
(B) Fine engraving
(C) Railway platform
(D) Auditoriums.
11. Which of the following lamp gives nearly monochromatic light ?
(A) Sodium vapor lamp
(B) GLS lamp
(C) Tube light
(D) Mercury vapor lamp.
12. The illumination level in houses is in the range
(A) 10-20 lumen/m2
(B) 30 - 50 lumen/m2
(C) 40-75 lumen/m2
(D) 100-140 lumen/m2.
13. Luminous efficiency of a fluorescent tube is
(A) 5- 10 lumens/watt
(B) 15-20 lumens/watt
(C) 30 - 40 lumens/watt
(D) 60 - 65 lumens/watt.
14. One lumen per square meter is the same as
(A) One lux
(B) One candela
(C) One foot candle
(D) One lumen meter.
15. Standard wattage of 3 ft. fluorescent tube is
(A) 10 W
(B) 40 W
(C) 65 W
(D) 100 W.
16. For the same wastage which lamp is cheapest ?
(A) Sodium vapor lamp
(B) Mercury vapor lamp
(C) Fluorescent tube
(D) GLS lamps.
17. Optical instruments used for the comparison of candle powers of different sources arc known as
(A) Candle meters
(B) Radio meters
(C) Bunsen meter
(D) Photo meter.
18. Which photometer is used for comparing the lights of different colors ?
(A) Bunson photometer
(B) Grease spot photometer
(C) Lummer Brodhum photometer
(D) Guilds Flicker Photometer
19. Which photometer depends for its operation on Lambert's cosine law ?
(A) Macbeth lllumino meter
(B) Trotter Illumination Photometer
(C) Lummer Brodhum Photometer
(C) Guild's Flicker Photometer.
20. Which photometer depends for its operation on Inverse Square Law ?
(A) Guilds Flicker Photometer
(B) Lummer Brodhum Photometer
(C) Macbeth llluminometer
(D) Trotter Illumination Photometer.
21. The color temperature of day light is around
(A) 50 K
(B) 160 K
(C) 600 K
(D) 6000 K.
22. Light is produced in electric discharge lamps by
(A) heating effect of current
(B) magnetic effect of current
(C) ionization in a gas or vapor
(D) carbon electrodes.
23. Lumen/watt is the unit of
(A) Light flux
(B) Luminous intensity
(C) Brightness
(D) Luminous efficiency.
24. Candela is-the unit for
(A) Light flux
(B) Luminous intensity
(C) Brightness
(D) Luminous efficiency.
25. Which gas is sometimes used in filament lamps ?
(A) Argon
(B) Krypton
(C) Nitrogen
(D) Carbon dioxide.
26. Which bulb operates on lowest power ?
(A) Night bulb
(B) Neon bulb
(C) GLS bulb
(D) Torch bulb.
27. The output of a tungsten filament lamp depends on
(A) size of lamp
(B) size of shell
(C) temperature of filament
(D) all of the above.
28. A zero watt lamp consumes
(A) no power
(B) about 5 to 7 W power
(C) about 15 to W power
(D) about 25 to 30 W power.
29. Melting temperature of tungsten is
(A) 2000°K
(B) 2500°K
(C)2655°K
(D) 3655°K.
30. The life of incandescent lamp is expected to be
(A) 100 hours
(B) 200 hours
(C) 1000 hours
(D) 10000 hours.
31. The source of illumination for a cinema projector is
(A) Incandescent lamp
(B) Mercury vapor lamp
(C) Sodium lamp
(D) Carbon arc lamp.
32. Sodium vapor lamps need ionization potential of about
( A) 5 volts
(B) 50 volts
(C) 100 volts
(D) 112 volts.
33. When a sodium vapor lamp is switched on, initially the color is
(A) Pink
(B) Yellow
(C) Green
(D) Blue.
34. In a sodium vapor lamp the discharge is first started in the
(A) neon gas
(B) nitrogen gas
('C) argon gas
(D) krypton gas.
35. A auto transformer used with sodium vapor lamp should have
(A) high efficiency
(B) high step-up ratio
(C) high step-down ratio
(D) high leakage reactance.
36. The capacitor used in auto transformer circuit for sodium vapor lamps, is for
(A) protection against accidental power failure
(B) controlling illumination level of the lamp
(C) for regulating discharge voltage
(D) for improving the power factor of the circuit.
37. A mercury vapor lamp gives
(A) pink light
(B) yellow light
(C) greenish blue light
(D) white light.
38. Under the influence of fluorescent lamps sometimes the wheels of rotating machinery appear to be stationary. This is due to the
(A) fluctuations
(B) luminescence effect
(C) stroboscopic effect
(D) low power factor.
39. Power factor is highest in case of
(A) Mercury arc lamp
(B) Sodium vapor lamps
(C) Tube lights
(D) GLS lamps.
40. Which of the following electric discharge lamp gives highest lumens/watt
(A) Sodium vapor lamp
(B) Neon lamp
(C) Mercury lamp at low pressure
(D) Mercury vapor at high pressure.
41. The solid angle subtended at the center of a hemisphere of diameter D will be
(A) 4πD
(B) 2πD
(C) 2π
(D)4π.
42. Which one of the following is a cold cathode lamp ?
(A) Sodium lamp
(B) Neon lamp
(C) GSL lamp
(D) Tube light.
43. In a mercury vapor lamp light red objects appear black due to
(A) high wavelength of red objects
(B) color mixing
(C) absence of red light from lamp radiation
(D) absorption of red light by the lamp radiation.
44. The flicker effect of fluorescent lamp is more pronounced at
(A) lower voltages
(B) higher voltages
(C) lower frequencies
(D) higher frequencies.
45. The frequency of flickers in a fluorescent lamp at 220 V, 50 Hz supply will be
(A) 25 per second
(B) 50 per second
(C) 100 per second
(D) 220 per second.
46. Wavelength of green color is nearly
(A) 4000 A
(B) 4500 A
(C) 5000 A
(D) 5500 A.
47. One Angstrom is
(A) 10-6 meter
(B)10-8 meter
(C) 10-8 cm
(D) 10-8 mm.
48. Which of the following color has wave-length between green and color ?
(A) Yellow
(B) Blue
(C) Violet
(D) None.
49. The purpose of providing a choke in a tube light is
(A) to eliminate corona effects
(B) to avoid radio interference
(C) to improve power factor
(D) to limit current to appropriate value.
50. A 60 W lamp given a luminous flux of 1500 lumen. Its efficiency is
(A) 1500 lumen/watt
(B) 250 lumen/watt
(C) 25 lumen/watt
(D) 2.5 lumen/watt.
51. One lux is the same as
(A) one lumen/sq. cm
(B) one lumen/sq. m
(C) one lumen/100 sq. m
(D) one lumen/1000 sq. m.
52. The vacuum inside an incandescent lamp is of the order of
(A) 10-2 mm Hg
(B) 10-3 mm Hg
(C) 10-4 mm Hg
(D) 10-5 mm Hg.
53. Which of the following application does not need ultra-violet lamps ?
(A) Medical purposes
(B) Aircraft cockpit dashboard lighting
(C) Car lighting
(D) Blue print machines.
54. When using ultra-violet lamps the reflector for maximum should be made of
(A) aluminium
(B) copper
(C) leaf
(D) glass.
55. Which of the following combination of gas is filled in lamp and the resulting color is incorrect?
(A) Neon-red
(B) Nitrogen-buff
(C) Carbon dioxide - day light white
(D) Magnesium-white.
56. Which of the, following vapors/gas will give yellow color in a filament lamp ?
(A) Helium
(B) Mercury
(C) Sodium
(D) Magnesium.
57. Which of the following phosphor produces green color
(A) Zinc silicate
(B) Cadmium borate
(C) Magnesium tungstate
(D) Calcium halo phosphate.
58. If d is the distance of a surface from a source, the illumination of the surface will vary as
(A) d
(B) 2d
(C)1/d
(D) 1/ d 2
59. The level of illumination on surface least depends on
(A) candle power of the source
(B) distance of the source
(C) type of reflector used
(D) ambient temperature.
60. The level of illumination from a 100 W incandescent lamp will not increase by
(A) increasing the supply voltage
(B) increasing filament temperature
(C) increasing glass shell diameter.
61. The rate of evaporation of tungsten filament in a lamp depends on
(A) glass shell diameter
(B) exhaust tube diameter
(C) vapor pressure inside
(D) none of the above.
62. A gas filled filament bulbs, the gas used is
(A) oxygen
(B) helium
(C) nitrogen
(D) ozone.
63. Heat from the filament of a lamp is transmitted to the surrounding- mainly through
(A) conduction
(B) convection
(C) radiation.
64. In a fluorescent tube circuit, choke acts as
(A) starter
(B) power factor improving device
(C) source of heat
(D) current limiting device.
65. When a fluorescent lamp is to be operated on dc which of the following additional device must be incorporated in the circuit ?
(A) Condenser
(B) Transformer
(C) Resistance
(D) Inductance.
66. For same rating the amount of radiant heat produced in which of the following lamp is the least ?
(A) Fluorescent lamp
(B) Filament lamp
(C) Sodium vapor lamp
(D) Mercury vapor lamp.
67. The amount of radiant heat produced by a fluorescent lamp is nearly what percent of that of a filament lamp of same rating
(A) 80%
(B) 60%
(C)40%
(D) 20%.
68. Which of the following lamp gives nearly ultra-violet light ?
(A) Vacuum type filament lamp
(B) Nitrogen filed filament lamp
(C) Argon filled filament lamp
(D) Carbon arc lamp.
69. Luminous flux is
(A) rate of energy radiation in the form of light waves
(B) light energy radiated by sun
(C) part of light energy, radiated by sun which is received on earth
(D) none of the above.
70. Match the following Column I Column II
(a) Luminous flux (i) Candela
(b) Luminous (ii) Candle power x intensity Solid angle
(c) Lumen (iii) Lumens/W steredians
(d)Candle power (iv) Lumens.
(A)a-(i), b-(ii), c-(iii),d-(iv)
(B) a-(iv), b-(i), c-(ii), d-(iii)
(C) a-(i), b-(iv), c-(ii), d-(iii)
(D) a - (iv), b - (iii), c- (i), d - (ii).
71. According to Lambert's law, the illumination on a surface is proportional to
(A) cos2 θ
(B)cos3θ
(C)1/cos3θ
(D) 1/ cos2 θ.
72. A lamp has a mean spherical candle power of 25, the total flux of light from the lamp is
(A) 25 lumens
(B) 25 π lumens
(C) 314 lumens
(D) 625 lumens.
73. Which of the following material can be used for the filaments in incandescent lamps is
(A) carbon
(B) tungsten
(C) tantalum
(D) any of the above.
74. The melting point of carbon is
(A) 1800°C
(B) 2200°C
(C) 3500°C
(D) 5500° C.
75. Which of the following filament material has the lowest melting point ?
(A) Carbon
(B) Tungsten
(C) Tantalum
(D) Osmium.
76. The operating characteristics of an incandescent lamp arc materially affected by departure from its normal operating voltage. The total number of lumens given out by the lamp increases with the increase in operating voltage and the relation between them is : Lumens output α Vn where n is a constant. The value of n for tungsten varies for
(A) 0.5 to 0.75
(B) 1.5 to 2.5
(C) 4 to 5
(D) 8 to 10
77. Filament lamps operate normally at a power factor of
(A) 0.5 leading
(B) 0.5 lagging
(C) unity
(D) 0.8 lagging.
78. Neon gas in sodium vapor lamp
(A) changes the color of light
(B) acts as a shield around the filament
(C) assists in developing enough heat to vaporize the sodium
(D) prevents vaporization of filament.
79. Which of the following is a cold cathode lamps ?
(A) Sodium vapor lamp
(B) High pressure mercury vapor lamp
(C) Low pressure mercury vapor lamp
(D) Neon lamp.
80. In fluorescent tubes ballast resistance is connected in series with the choke
(A) when supply frequency is low
(B) to reduce radio interference
(C) when tube operates on dc supply
(D) to reduce stroboscope effects.
81. While comparing tungsten filament lamps with fluorescent tubes, all of the following are the advantages in favor of tungsten filament lamp EXCEPT
(A) Longer life
(B) Less costly
(C) More brightness
(D) Simple installation.
Questions 83 to 85 refer to data given below: The 220 V lamps, one of 60 W and the other of 75 W arc connected in series across a 440 V supply.
82. The potential difference across 60 W lamp will be
(A) 195 V
(B) 220 V
(C) 245 V
(D) 440 V.
83. The potential difference across 75 watt lamp will be
(A) 195 V
(B) 220 V
(C) 245 V
(D) 440 V.
84. Assuming candle power to be proportional to fourth power of the voltage, the candle power of 60 W lamps under above conditions as a percentage of its value under normal operation at 220 V will be
(A) 110%
(B) 1549%
(C)220%
(D) 440%.
85. Which of the following lamp has last capacity to sustain voltage fluctuations ?
(A) sodium vapor lamp
(B) fluorescent lamp
(C) incandescent lamp
(D) mercury vapor lamp.
86. In neon signs argon gas is used for
(A) yellow color
(B) blue color
(C) red color
(D) green color.
87. In neon signs, helium is used for
(A) yellow color
(B) green color
(C) red color
(D) blue co lour.
88. In neon signs, neon with a mixture of mercury gives
(A) green color
(B) blue color
(C) red color
(D) yellow color.
89. The electrodes of neon tubes work at
(A) very low temperatures
(B) ordinary voltages
(C) 400 to 440 volts
(D) 2000 to 6000 volts.
90. Glare may result from
(A) excessive lighting contrast in the field of vision
(B) excessive luminance
(C) either of (A) or (B) above
(D) none of the above
91. To avoid glare
(A) object should be viewed from a distance
(B) object should be viewed from a close vicinity
(C) object should be moved constantly
(D) viewer should move constantly.
92. The light output of GLS lamps is normally in the range
(A) 10 to 18 lumens/watt
(B) 50 to 80 lumens/watt
(C) 100 to 180 lumens/watt
(D) 200 to 300 lumens/watt.
93. Nitrogen or argon is filled in GLS lamps to
(A) reduce the glare
(B) improve efficiency
(C) change the color of light
(D) retard evaporation of tungsten filament.
94. In case of frosted GLS lamps, frosting of shell is done by
(A) ozone
(B) ammonia
(C) acid etching
(D) salt water.
95. The luminous flux reaching the working plane least depends on
(A) the lumen output of the lamps
(B) proportion of the room
(C) reflectance of internal surfaces
(D) color of the working plane surface.
96. Which of the following lamp gives nearly monochromatic light ?
(A) Sodium vapor lamp
(B) GLS lamp
(C) Tube light
(D) Mercury vapor lamp.
97. Materials which reflect all wavelengths in the light spectrum appear to be
(A) black to white
(B) transparent
(C) opaque
(D) green to red.
98. An object which appears red to the eyes, absorbs
(A) green radiations
(B) blue radiations
(C) violet radiations
(D) all of the above.
99. Glare is the result of
(A) very low luminance
(B) normal luminance
(C) excessive luminance
(D) none of the above.
100. Glow lamps
(A) have cold cathode
(B) have hot cathode
(C) cannot withstand shocks
(D) consume high power.
101. The illumination required for normal reading is around
(A) 500 lumens/m2
(B) 300 - 400 lumens/m2
(C) 100 - 250 lumens/m2
(D) 60 - 100 lumens/m2.
102. Which of the following surface has the lowest reflection factor for white light ?
(A) Aluminium sheet
(B) White plaster work
(C) Blue curtains
(D) White oil paint
103. Which of the following glass transmits the maximum light ?
(A) Serrated glass
(B) Opalescent glass
(C) Clear glass
(D) Milk glass.
104. Which of the following glass transmits the least amount of light?
(A) Clear glass
(B) Serrated glass
(C) Milk glass
(D) Opalescent glass.
105. B-15 size cap for GLS lamp indicates that
(A) cap diameter is 15 mm
(B) cap is screw type
(C) cap is made of brass
(D) cap is filled by cement.
106. E-40 caps arc generally used for GLS lamps of wattage above
(A) 25 W
(B)100W
(C)300W
(D) 1000 W.
107. In case of GLS lamps as the supply voltage increases, which of the following decreases ?
(A) Lumen output
(B) Power consumption
(C) Life
(D) Efficiency.
108. The advantage of halogen lamp is
(A) no depreciation of light output
(B) increased operating temperature with increased luminous efficiency
(C) reduced dimensions of the lamp
(D) all of the above.
109. Halogen lamps are useful for the illumination of
(A) Sports grounds
(B) Parks
(C) Airports
(D) All of the above.
110. Coating or fluorescent lamps
(A) converts ultra-violet, radiations into visible light
(B) converts visible light into ultra-violet radiations
(C) reduces glare
(D) none of the above.
111. The light output of fluorescent lamps is around
(A) 10 lumens/watt
(B) 20 lumens/watt
(C) 70 lumens/watt
(D) 200 lumens/watt.
112. Which of the following is preferred for air conditioned spaces ?
(A) GLS lamp
(B) Fluorescent tube
(C) Mercury vapor lamp
(D) Sodium vapor lamp.
113. The normal life span of a fluorescent lamp is
(A) 500 hours
(B) 1000 hours
(C) 1500 hours
(D) 7500 hours.
114. The color of light depends on
(A) wavelength
(B) frequency
(C) wavelength and frequency
(D) wavelength, frequency speed and intensity.
115. The disadvantage of fluorescent lamps as compared to GLS lamps is
(A) noise in choke
(B) stroboscope effect
(C) high cost
(D) all of the above.
116. In case of a fluorescent lamp if only the ends of the lamp remain lighted it indicates
(A) a short circuited starter
(B) a defective choke
(C) a defective lube
(D) defective wiring.
117. Blinking of a fluorescent tube may be due to
(A) low circuit voltage
(B) low ballast rating
(C) low temperature
(D) any of the above.
118. Radio interference generally results due to
(A) GLS lamps
(B) Halogen lamps
(C) Fluorescent lamps
(D) Sodium lamps.
119. A fluorescent tube can be operated on
(A) AC only
(B) DC only
(C) Both AC as well as DC.
120. The ignition voltage for sodium lamps is
(A) 100 to 150 volts .
(B) 200 to 220 volts
(C) 400 to 440 volts
(D) 400 to 600 volts.
121. A leak transformer is provided with
(A) frosted GLS lamps
(B) high wattage GLS lamps
(C) fluorescent lamps
(D) sodium lamps.
122. Leak transformer in sodium lamps initially provides
(A) low voltage
(B) high current
(C) high voltage
(D) none of the above.
123. The color of sodium lamp is
(A) blue
(B) yellow
(C) red
(D) white.
124. Sodium lamps are used for:
(A) reading rooms
(B) street lights
(C) auditoria
(D) libraries.
125. The average life of sodium lamps is around
(A) 1000 hours
(B) 2500 hours
(C) 6000 hours
(D) 12000 hours.
126. High pressure mercury vapor light contains
(A) yellow color
(B) bluish white color
(C) red color
(D) white color.
127. The average life high pressure mercury vapor lamps is
(A) 500 hours
(B) 1000 hours
(C) 9000 hours
(D) 20,000 hours.
128. High pressure mercury vapor lamps are generally used in
(A) factories
(B) railway yards
(C) shopping centers
(D) all of the above.
129. A substance which changes its electrical resistance when illuminated by light is called
(A) photovoltaic
(B) photoelectric
(C) photo-conductive
(D) none of the above.
130. Wavelength for blue color
(A) 4400 A
(B) 5250 A
(C) 6150 A
(D) 5950 A.
131. Radio interference from a fluorescent lamp can be reduced by
(A) putting two lamps in parallel
(B) eliminating choke
(C) putting a capacitor across the lamp
(D) none of the above.
132. Dimming systems for lights are used in
(A) theatres
(B) auditoriums
(C) ball room
(D) all of the above.
133. Which of the following can be used as a light dimming device ?
(A) Auto transformer
(B) Variable reaction
(C) SCR
(D) Any of the above.
134. Which of the following is difficult to adopt for dimming ?
(A) GLS lamps
(B) Cold cathode lamps
(C) Fluorescent lamps
(D) All of the above.
135. Heat from light source is particularly of importance while
(A) designing for illumination level
(B) designing for floor space utilization
(C) designing for air conditioning
(D) all of the above.
136. In electric discharge lamps for stablizing the arc
(A) a condenser is connected in parallel to supply
(B) a condenser is connected in series to supply
(C) a variable resistor is connected in the circuit
(D) a reactive choke is connected in series with supply.
137. The lens of the eye to focuses an image on the
(A) corona
(B) membrane
(C) calorie
(D) retina.
138. The sensors in the eye arc known as
(A) rods and cones
(B) wires and nerves
(C) retina and antenna
(D) high and low.
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