Electric Illumination MCQs

1. Radiant efficiency of the luminous source depends on

(A) the wavelength of light rays
(B) the temperature of the source
(C) the shape of the source
(D) all of the above

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Answer. B

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

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Answer. A

3. Carbon arc lamps are commonly used in

(A) domestic lighting
(B) street lighting
(C) cinema projectors
(D) photography.

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Answer. C

4. The unit of solid angle is

(A) solid angle
(B) radian
(C) steradian
(D) candela.

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Answer. C

5. Candela is the unit of

(A) Luminous flux
(B) Luminous intensity
(C) Wavelength
(D) None of the above.

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Answer. B

6. The unit of luminous flux is

(A) steradian
(B) candela
(C) lumen
(D) lux.

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Answer. C

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.

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Answer.D

8. Which curve represents the life of the lamp?

(A) curve A
(B) curve B
(C) curve C
(D) curve D.

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Answer. B

9. Illumination level required for precision work is around

(A) 50 lm/m2
(B) 100 lm/m2
(C) 200 lm/m2
(D) 500 lm/m2.

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Answer.D

10. Which of the following will need the highest level of illumination?

(A) Proof reading
(B) Bed rooms
(C) Hospital wards
(D) Railway platforms.

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Answer. A

11. Which of the following will need the lowest level of illumination?

(A) Displays
(B) Fine engraving
(C) Railway platform
(D) Auditoriums.

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Answer. C

12. Which of the following lamp gives nearly monochromatic light?

(A) Sodium vapor lamp
(B) GLS lamp
(C) Tube light
(D) Mercury vapor lamp.

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Answer. A

13. 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.

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Answer.D

14. 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.

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Answer.D

15. One lumen per square meter is the same as

(A) One lux
(B) One candela
(C) One foot candle
(D) One lumen meter.

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Answer. A