1. The building manager who is helping you get set up mentions that he recently
ID: 1659035 • Letter: 1
Question
1. The building manager who is helping you get set up mentions that he recently replaced all the incandescent (filament) bulbs in the building with these LED fixtures and is saving the university a bunch of money. He mentions that the old incandescent bulbs were inefficient, only providing 15 lumens for every 1 Watt of electric power. He picks up an old incandescent bulb, which is labeled ‘100 W', holds it next to the light fixture, and exclaims: "This new light fixture provides 10 times the illumination of the incandescent bulb! I checked all around the room with my photometer! What is the total light energy output of the LED bulb, expressed in lumens? (2)Explanation / Answer
The incandescent bulb provides 15 lumens/W
100 W bulb provides = 15 x 100 = 1500 lumens
The new LED fixture provides 10 times more illumination. Hence the total light energy output is 1500*10 lumens = 15000 lumens
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