46. 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.
47. Wavelength of green color is nearly
(A) 4000 A
(B) 4500 A
(C) 5000 A
(D) 5500 A
48. One Angstrom is
(A) 10-6 meter
(B)10-8 meter
(C) 10-8 cm
(D) 10-8 mm.
49. Which of the following color has wavelength between green and colour?
(A) Yellow
(B) Blue
(C) Violet
(D) None.
50. 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.
51. 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.
52. 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.
53. 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.
54. 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.
55. When using ultra-violet lamps the reflector for maximum should be made of
(A) aluminium
(B) copper
(C) leaf
(D) glass
56. 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.
57. Which of the, following vapors/gas will give yellow color in a filament lamp?
(A) Helium
(B) Mercury
(C) Sodium
(D) Magnesium.
58. Which of the following phosphor produces green color
(A) Zinc silicate
(B) Cadmium borate
(C) Magnesium tungstate
(D) Calcium halo phosphate.
59. 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
60. 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.
