MCQ ON ILLUMINATION

Objective Questions

Short notes

Objective questions (Answers are given below)

Candela is the unit of
(a) flux
(b) luminous intensity
(c) illumination
(d) luminance.
The unit of illuminance is
(a) lumen
(b) cd/m2
(c) lux
(d) steradian.
The illumination at various points on a
horizontal surface illuminated by the same
source varies as
(a) cos3
θ
(b) cos θ
(c) 1/r2
(d) cos2 θ.
The M.S.C.P. of a lamp which gives out a total
luminous flux of 400 π lumen is
OBJECTIVE TESTS – 49
…………………. candela.
(a) 200
(b) 100
(c) 50
(d) 400.
A perfect diffuser surface is one that
(a) diffuses all the incident light
(b) absorbs all the incident light
(c) transmits all the incident light
(d) scatters light uniformly in all directions.
The direct lighting scheme is most efficient but
is liable to cause
(a) monotony
(b) glare
(c) hard shadows
(d) both (b) and (c).
Total flux required in any lighting scheme depends
inversely on
(a) illumination

(b) surface area
(c) utilization factor
(d) space/height ratio

Floodlighting is NOT used for ……………..
purposes.
(a) reading
(b) aesthetic
(c) advertising
(d) industrial.
Which of the following lamp has minimum
initial cost of installation but maximum
running cost ?
(a) incandescent
(b) fluorescent
(c) mercury vapour
(d) sodium vapour.
An incandescent lamp can be used
(a) in any position
(b) on both ac and dc supply
(c) for street lighting
(d) all of the above.
The average working life of a fluorescent lamp
is about…………………… hours.
(a) 1000
(b) 4000
(c) 3000
(d) 5000.
The luminous efficiency of a sodium vapour
lamp is about ……………….. lumen/watt.
(a) 10
(b) 30
(c) 50
(d) 70
Which of the following statements is correct?
(a) Light is a form of heat energy
(b) Light is a form of electrical energy
(c) Light consists of shooting particles
(d) Light consists of electromagnetic waves
Luminous efficiency of a fluorescent tube is
(a) 10 lumens/watt
(b) 20 lumens/watt
(c) 40 lumens/watt
(c) 60 lumens/watt
Candela is the unit of which of the following?
(a) Wavelength
(b) Luminous intensity
(c) Luminous flux
(d) Frequency
Colour of light depends upon
(a) frequency
(b) wave length
(c) both (a) and (b)
(d) speed of light
Illumination of one lumen per sq. metre is
called …….
(a) lumen metre
(b) lux
(c) foot candle
(d) candela
A solid angle is expressed in terms of …….
(a) radians/metre
(b) radians
(c) steradians
(d) degrees
The unit of luminous flux is ……..
(a) watt/m2
(b) lumen
(c) lumen/m2
(d) watt
Filament lamps operate normally at a power
factor of
(a) 0.5 lagging
(b) 0.8 lagging
(c) unity
(d) 0.8 leading
The filament of a GLS lamp is made of
(a) tungsten
(b) copper
(c) carbon
(d) aluminium
Find diameter tungsten wires are made by
(a) turning
(b) swaging
(c) compressing
(d) wire drawing
What percentage of the input energy is
radiated by filament lamps?
(a) 2 to 5 percent
(b) 10 to 15 percent
(c) 25 to 30 percent
(d) 40 to 50 percent
Which of the following lamps is the cheapest
for the same wattage?
(a) Fluorescent tube
(b) Mercury vapour lamp
(c) GLS lamp
(d) Sodium vapour lamp
Which of the following is not the standard
rating of GLS lamps?
(a) 100 W
(b) 75 W
(c) 40 W
(d) 15 W
In houses the illumination is in the range of
(a) 2–5 lumens/watt
(b) 10–20 lumens/watt

‘‘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) Lambert’s cosine law
(b) Planck’s law
(c) Bunsen’s law of the illumination
(d) Macbeth’s law of illumination
The colour of sodium vapour discharge lamp
is
(a) red
(b) pink
(c) yellow
(d) bluish green
Carbon arc lamps are commonly used in
(a) photography
(b) cinema projectors
(c) domestic lighting
(d) street lighting
Desired illumination level on the working
plane depends upon
(a) age group of observers
(b) whether the object is stationary or moving
(c) Size of the object to be seen and its
distance from the observer
(d) whether the object is to be seen for longer
duration or shorter duration of time
(e) all above factors
On which of the following factors dies the
depreciation or maintenance factor depend?
(a) Lamp cleaning schedule
(b) Ageing of the lamp
(c) Type of work carried out at the premises
(d) All of the above factors
In lighting installating using filament lamps
1% voltage drop results into
(a) no loss of light
(b) 1.5 percent loss in the light output
(c) 3.5 percent loss in the light output
(d) 15 percent loss in the light output
For the same lumen output, the running cost
of the fluorescent lamp is
(a) equal to that of filament lamp
(b) less than that of filament lamp
(c) more than that of filament lamp
(d) any of the above
For the same power output
(a) high voltage rated lamps will be more
sturdy
(b) low voltage rated lamps will be more
sturdy
(c) both low and high voltage rated lamps
will be equally sturdy
The cost of a fluorescent lamp is more than
that of incandescent lamp because of which of
the following factors?
(a) More labour is required in its
manufacturing
(b) Number of components used is more
(c) Quantity of glass used is more
(d) All of the above factors
Filament lamp at starting will take current
(a) less than its full running current
(b) equal to its full running current
(c) more than its full running current
A reflector is provided to
(a) protect the lamp
(b) provide better illumination
(c) avoid glare
(d) do all of the above
The purpose of coating the fluorescent tube
from inside with white power is
(a) to improve its life
(b) to improve the appearance
(c) to change the colour of light emitted to
white
(d) to increase the light radiations due to
secondary emissions
……. will need lowest level of illumination.
(a) Audiotoriums
(b) Railway platform
(c) Displays
(d) Fine engravings
Due to moonlight, illumination is nearly
(a) 3000 lumens/m2
(b) 300 lumens/m2
(c) 30 lumens/m2
(d) 0.3 lumen/m2
Which of the following instruments is used for
the comparison of candle powers of different
sources?
(a) Radiometer
(b) Bunsen meter
(c) Photometer
(d) Candle meter
……. photometer is used for comparing the
lights of different colours?
(a) Grease spot
(b) Bunsen
(c) Lummer brodhum
(d) Guilds flicker
In the fluorescent tube circuit the function of
choke is primarily to
(a) reduce the flicker

(b) minimise the starting surge
(c) initiate the arc and stabilize it
(d) reduce the starting current

…… cannot sustain much voltage fluctuations.
(a) Sodium vapour lamp
(b) Mercury vapour lamp
(c) Incandescent lamp
(d) Fluorescent lamp
The function of capacitor across the supply to
the fluorescent tube is primarily to
(a) stabilize the arc
(b) reduce the starting current
(c) improve the supply power factor
(d) reduce the noise
…… does not have separate choke
(a) Sodium vapour lamp
(b) Fluorescent lamp
(c) Mercury vapour lamp
(d) All of the above
In sodium vapour lamp the function of the leak
transformer is
(a) to stabilize the arc
(b) to reduce the supply voltage
(c) both (a) and (b)
(d) none of the above
Most affected parameter of a filament lamp
due to voltage change is
(a) wattage
(b) life
(c) luminous efficiency
(d) light output
In electric discharge lamps for stabilizing the
arc
(a) a reactive choke is connected in series
with the supply
(b) a condenser is connected in series to the
supply
(c) a condenser is connected in parallel to the
supply
(d) a variable resistor is connected in the
circuit
For precision work the illumination level
required is of the order of
(a) 500-1000 lumens/m2
(b) 200-2000 lumens/m2
(c) 50-100 lumens/m2
(d) 10-25 lumens/m2
…… is a cold cathode lamp.
(a) Fluorescent lamp
(b) Neon lamp
(c) Mercury vapour lamp
(d) Sodium vapour lamp
In case of …… least illumination level is
required.
(a) skilled bench work
(b) drawing offices
(c) hospital wards
(d) find machine work
For normal reading the illumination level
required is around
(a) 20-40 lumens/m2
(b) 60-100 lumens/m2
(c) 200-300 lumens/m2
(d) 400-500 lumens/m2
In electric discharge lamps light is produced
by
(a) cathode ray emission
(b) ionisation in a gas or vapour
(c) heating effect of current
(d) magnetic effect of current
A substance which change its electrical
resistance when illuminated by light is
called …….
(a) photoelectric
(b) photovoltaic
(c) phatoconductive
(d) none of the above
In case of …… power factor is the highest.
(a) GLS lamps
(b) mercury arc lamps
(c) tube lights
(d) sodium vapour lamps
A mercury vapour lamp gives ….. light.
(a) white
(b) pink
(c) yellow
(d) greenish blue
Sometimes the wheels of rotating machinery,
under the influence of fluorescent lamps
appear to be stationary. This is due to the
(a) low power factor
(b) stroboscopic effect
(c) fluctuations
(d) luminescence effect
Which of the following bulbs operates on least
power?
(a) GLS bulb
(b) Torch bulb
(c) Neon bulb
(d) Night bulb
The flicker effect of fluorescent lamps is more
pronounced at
(a) lower frequencies
(b) higher frequencies
(c) lower voltages
(d) higher voltages

Which of the following application does not
need ultraviolet lamps?
(a) Car lighting
(b) Medical purposes
(c) Blue print machine
(d) Aircraft cockpit dashboard lighting

Which gas can be filled in GLS lamps?
(a) Oxygen
(b) Carbon dioxide
(c) Xenon
(d) Any inert gas

(b) 2. (c) 3. (a) 4. (b) 5. (d) 6. (d) 7. (c) 8. (a) 9. (a) 10. (d) 11.(b) 12. (d) 13. (d) 14. (d) 15. (b) 16. (c) 17. (b) 18. (c) 19. (b) 20. (c ) 21.(a) 22. (d) 23. (b) 24. (c) 25. (b) 26. (d) 27. (a) 28. (c) 29. (b) 30. (e) 29.(d) 32. (c) 33. (b) 34. (b) 35. (d) 36. (c) 37. (d) 38. (d) 39. (b) 40. (d) 41.(c) 42. (d) 43. (c) 44. (c) 45. (c) 46. (a) 47. (c) 48. (b) 49. (a) 50. (a) 51.(b) 52. (c) 53. (b) 54. (b) 55. (c) 56. (a) 57. (d) 58. (b) 59. (b) 60. (a) 61.(a) 62. (d)

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