Sivalingam Kts

40%
Flag icon
In 1902, a lightbulb with a tantalum filament produced 7 lumens per watt; in 2019, a dimmable LED light delivers 89 lm/W. That means that a lumen of electric light for a working-class household is now approximately 2,500 times more affordable than it was in the early 20th century.
Numbers Don't Lie: 71 Things You Need to Know About the World
Rate this book
Clear rating
Open Preview