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A class room measuring 10 m (L) × 8 m (B) × 2.7 m (H) requires an illumination level of 500 lux on the desk level using 40 W fluorescent lamps with rated output of 5000 lumens each. Assuming utilization factor of 0.5 and maintenance factor of 0.8, the number of lamps required is _________
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- 20
- 40
- 80
- 120
Correct Option: A
500 lux = 500 lumen/m2
Total lumen required = (500 lumen/m2) × (Area of the room) = 500 × 10 × 8
Lumen output of one lamp = 5000 lumen (given)
Actually the lumen output of the lamp will be less than 5000 lumen because of utilization factor and maintenance factor. So, net lumen output = 5000 × 0.5 × 0.8
| Required no. of lamps = | = | = 20 | ||
| lumen of on lamp | 5000 × 0.5 × 0.8 |
