01․ The range of visual spectrum is
The visual spectrum lies in between the UV spectrum on its left to Infra-red spectrum to its right. Its range is 380nm -760nm.
02․ Which lamp has a negative Colour Rendering Index (CRI)?
Low pressure sodium vapour lamp has a monochromatic spectrum and therefore has a negative CRI.
03․ A 1000 W bulb fitted with a reflector illuminates an area of 3 m x 3 m with an average illumination of 450 lux. If the bulb has and efficiency of 9 lumens / watt the efficiency of the reflector is
04․ What will be the total flux emitted by a source of 60 candle power?
Total flux = (4 X 3.14 X 60) lumens = 754.2 lumens.
05․ From a uniform light source having luminous intensity of 300 candelas, there exists a plane surface 15 m below. The value of illuminance at a point on the plane surface where the luminous flux rays are inclined at an angle of 30 to the surface is
From the laws of illumination,
Illuminance = Intensity × cosine of the angle of inclination of light rays/ Distance2
E = I Cosθ/d2 = 300 × cos 30/225 = 1.15 lux
06․ The solid angle subtended by an area of 2400 cm2 on the surface of a sphere of diameter 1.2 m is
07․ In illumination technology total lumens emitted by source / total lumens available after waste of light is equal to
Total lumens emitted by source / total lumens available after waste of light is equal to waste light factor. It is about 1.2 for rectangular area, 1.5 for irregular objects - statues, monuments etc.
08․ The illumination at a point 5 meters below a lamp in 6 lux. The candle power of the lamp is
09․ Which among the following lamps has the maximum burning hours?
LEDs have very high burning hours of about 500000 hours.
10․ A 200 candle power lamp is hung 4 m above the centre of circular area of 5 m diameter. The illumination at centre of the area is
According to law of inverse square the illumination can be given as,
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