In our daily life, the furniture should be put at a proper height.

First, the incandescent bulb should be installed above the desk a proper height, which is good to our eyesight. The proper height of 60 watt bulb should be 100 centimeters above the desk, and 40 watt bulb 65 centimeters, and 25 watt bulk 50 centimeters, and 15 watt bulk 30 centimeters. As to the fluorescent bulb, it is the same thing. The proper height of 40 watt bulb should be 150 centimeters, and 30 watt bulb 140 centimeters, and 20 watt bulb 110 centimeters, 8 watt bulb 55 centimeters.
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