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LIGHT BULB (19th century)
OIL LAMP (approx. 15 000 B.C.)
FLUORESCENT LAMP (20th century)
LED (21st century)
0,1 lm/W
300 lm/W
70 lm/W
16 lm/W
Illus
trat
ion:
© Jo
han
Jarn
esta
d/Th
e Ro
yal S
wed
ish
Acad
emy
of S
cien
ces