Your light bulb makes light in one of two very different ways: a white-hot wire, or a tiny chip. I zoomed into both.
An old bulb pushes electricity through a thin coiled tungsten wire. The wire resists the current and heats up to about 2,500°C (about 4,500°F), hot enough to glow. But about 90% of the power leaves as heat, and only about 10% becomes light.
An LED has no hot wire. Inside is a tiny semiconductor chip: one layer with spare electrons, one with "holes" (missing electrons). Electricity pushes them together at the junction, and each time an electron drops into a hole it releases a photon, a tiny flash of light.
How far the electron drops sets the color of the light. And here's the part most people don't know: the chip inside a white LED is blue. A yellow coating (a phosphor) turns some of that blue into yellow, and blue plus yellow looks white to your eye.
Because almost nothing is wasted as heat, a 9-watt LED gives about the same light (800 lumens) as a 60-watt bulb, and it can last up to 25 times longer.
Episode 8 of "How it works": everyday tech, zoomed all the way in.
Sources:
- US Department of Energy, Lighting IQ: https://www.energy.gov/quiz-test-your-lighting-iq
- DOE Energy Saver lighting fact sheet: https://www.energy.gov/sites/default/files/2021-08/ES-EE%20Lighting_080921.pdf
- ENERGY STAR, Learn About Brightness (60 W = 800 lumens): https://www.energystar.gov/products/light_bulbs/learn-about-brightness
- Nobel Prize in Physics 2014, how an LED works: https://www.nobelprize.org/prizes/physics/2014/popular-information/
- US DOE, LED Basics (white light from blue LEDs + phosphor): https://www.energy.gov/eere/ssl/led-basics
Did you know the chip in a white LED is blue? Tell me in the comments.
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I'm Haris, a systems engineer. I make short videos about the tech you use every day.
More of my work: https://bytefy.in
#lightbulb #led #howitworks #physics #technology #shorts
