Illumination MCQ Question and Answer

1.Which of the following statements is correct?

  • ALight is a form of heat energy
  • BLight is a form of electrical energy
  • CLight consists of shooting particles
  • DLight consists of electromagnetic waves
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Correct Answer : (D)

Light consists of electromagnetic waves

Explanation:

2.Luminous efficiency of a fluorescent tube is

  • A10 lumen/watt
  • B20 lumen/watt
  • C40 lumen/watt
  • D60 lumen/watt
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Correct Answer : (D)

60 lumen/watt

Explanation:

Luminous efficiency of a fluorescent tube is 60 lumen/watt. Luminous efficiency is the ratio of luminous flux output to input power. Its unit is Lumen/Watt.

3.Candela is the unit of which of the following?

  • AWavelength
  • BLuminous intensity
  • CLuminous flux
  • DFrequency
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Correct Answer : (B)

Luminous intensity

Explanation:

Candela is the unit of Luminous intensity.  Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle. The SI unit of luminous intensity is Luminous flux per unit solid angle or Lumen per Steradian or Candela.

4.Colour of light depends upon

  • AFrequency
  • BWave length
  • CBoth (a) and (b)
  • DSpeed of light
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Correct Answer : (C)

Both (a) and (b)

Explanation:

5.Illumination of one lumen per sq. meter is called  ____________

  • ALumen meter
  • BLux
  • CFoot candle
  • DCandela
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Correct Answer : (B)

Lux

Explanation:

Illumination of one lumen per sq. meter is called Lux. One lux is equal to one lumen per square metre.

6.A solid angle is expressed in terms of  ____________

  • ARadians/metre
  • BRadians
  • CSteradians
  • DDegrees
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Correct Answer : (C)

Steradians

Explanation:

A solid angle is expressed in terms of Steradians.

7.The unit of luminous flux is  ___________

  • AWatt/sq. Metre
  • BLumen
  • CLumen/sq. Metre
  • DWatt
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Correct Answer : (B)

Lumen

Explanation:

The unit of luminous flux is Lumen.

8.Filament lamps operate normally at a power factor of

  • A0.5 lagging
  • B0.8 lagging
  • CUnity
  • D0.8 leading
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Correct Answer : (C)

Unity

Explanation:

9.The filament of a GLS lamps is made of

  • ATungsten
  • BCopper
  • CCarbon
  • DAluminium
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Correct Answer : (A)

Tungsten

Explanation:

10.Fine diameter tungsten wires are made by

  • ATurning
  • BSwaging
  • CCompressing
  • DWire drawing
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Correct Answer : (D)

Wire drawing

Explanation:

11.What percentage of the input energy is radiated by filament lamps?

  • A2 to 5 percent
  • B10 to 15 percent
  • C25 to 30 percent
  • D40 to 50 percent
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Correct Answer : (B)

10 to 15 percent

Explanation:

10 to 15 percent of the input energy is radiated by filament lamps.

12.Which of the following lamps is the cheapest for the same wattage?

  • AFluorescent tube
  • BMercury vapour lamp
  • CGLS lamp
  • DSodium vapour lamp
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Correct Answer : (C)

GLS lamp

Explanation:

13.Which of the following is not the standard rating of GLS lamps?

  • A100 W
  • B75 W
  • C40 W
  • D15 W
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Correct Answer : (B)

75 W

Explanation:

14.In house the illumination is in the range of 

  • A2 – 5 lumens/watt
  • B10 – 20 lumens/watt
  • C35 – 45 lumens/watt
  • D60 – 65 lumens/watt
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Correct Answer : (D)

60 – 65 lumens/watt

Explanation:

15.“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

  • ALambert’s cosine law
  • BPlanck’s law
  • CBunsen’s law of the illumination
  • DMacbeth’s law of illumination
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Correct Answer : (A)

Lambert’s cosine law

Explanation:

16.The colour of sodium vapour discharge lamp is

  • ARed
  • BPink
  • CYellow
  • DBluish green
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Correct Answer : (C)

Yellow

Explanation:

The colour of sodium vapour discharge lamp is Yellow.

17.Carbon arc lamps are commonly used in

  • APhotography
  • BCinema projectors
  • CDomestic lighting
  • DStreet lighting
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Correct Answer : (B)

Cinema projectors

Explanation:

18.Desired illumination level on the working plane depends upon

  • AAge group observers and Whether the object is stationary or moving
  • BSize of the object to be seen and its distance from the observer
  • CWhether the object is to be seen for longer duration or shorter duration of time
  • DAll above factors
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Correct Answer : (D)

All above factors

Explanation:

19.On which of the following factors does the depreciation or maintenance factor depend?

  • ALamp cleaning schedule
  • BAgeing of the lamp
  • CType of work carried out at the premises
  • DAll of the above factors
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Correct Answer : (D)

All of the above factors

Explanation:

20.In lighting installation using filament lamps  1% voltage drop results into

  • ANo loss of light
  • B1.5 percent loss in the light output
  • C3.5 percent loss in the light output
  • D15 percent loss in the light output
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Correct Answer : (C)

3.5 percent loss in the light output

Explanation: