The most remarkable thing about this Veritasium piece is that it takes a ubiquitous object — the LED — and reveals it as a gateway to understanding some of the most fundamental physics in our daily lives. Derek Muller isn't just explaining what LEDs do; he's using them as a lens into how semiconductors actually work, from atomic band theory to the chemistry of gallium compounds.
The Fundamentals of Light Emission
Muller opens with the basic definition, writing, "LED stands for light emitting diode we use this symbol in engineering drawings for LEDs notice it looks very similar to a diode symbol except it has these arrows that indicate that light is being emitted." This is effective because it immediately visualizes what most people have never seen — the actual schematic symbol — making the technical accessible.
The piece's strongest contribution is its explanation of why different LEDs produce different colors. "We've received different colors depending on the wavelength of the photon in this range," Muller writes, explaining that human eyes can only perceive photons with wavelengths between 400 and 700 nanometers. This framing is smart because it turns a design feature — color variety — into a lesson about the visible spectrum.
Different colors aren't about the case; they're about what happens inside the semiconductor itself.
The Physics of the PN Junction
Muller then dives deeper, explaining that "inside the semiconductor we just have electrons combining with holes and releasing photons in the process." This is the core mechanism, but it's also where the piece becomes genuinely illuminating. He clarifies that standard diodes produce near-infrared light — invisible to humans — while LEDs deliberately emit within our visible range.
The explanation of band theory is remarkably clear for a video transcript: "the electron needs to lose some energy to be accepted into this lower band it does that by releasing a photon in Silicon it needs to lose around 1.1 electron volts." This connects directly to wavelength calculation, showing how material choice determines color output.
What makes this approach powerful is Muller using the LED as a concrete example to explain abstract quantum mechanics: electrons jumping between energy bands, photons being emitted during these transitions, and the specific voltages required for each material.
Practical Applications and Circuit Design
The piece then shifts to practical electronics. "If we try to connect this led to this nine volt battery it will instantly be destroyed inside the LED is a thin wire the battery will try to push so many electrons through this wire that it just breaks," Muller explains, showing why resistors are essential. He clarifies that "the resistor removes energy from the circuit to protect the LED it is literally turning the electrical energy into heat to remove it" — a useful analogy for non-engineers.
The explanation of forward bias — where "this creates an electric field which prevents more electrons moving across" — demonstrates how depletion regions work in both diodes and LEDs. For red LEDs specifically, Muller notes "it's much higher around 1.7 volts," distinguishing it from the typical diode barrier of 0.5 to 0.7 volts.
Color Mixing and Device Types
The piece covers various LED form factors — through-hole, SMD, high-powered for torches and floodlights — but also explains how colors are actually mixed: "this one is actually a blue LED it just has a layer of yellow phosphorus over it and that's because the yellow and blue light combined makes a white light." This connects directly to how RGB LEDs work with three separate red, green, and blue elements sharing terminals.
The bi-directional and four-pin RGB explanations show how engineers manipulate these components: "we can control the voltage and current to each led to make any color we wish."
Bottom Line
Muller's strongest move is using a simple household object — the LED — as a gateway into semiconductor physics. The piece's biggest vulnerability is its occasional lack of depth on certain claims, particularly around data broker references that feel inserted rather than organic to the core explanation. For readers wanting to understand not just what LEDs do, but why they work the way they do, this piece delivers substantial value through clear analogies and progressive complexity.
The most lasting insight? The LED's colored case is purely cosmetic — "the cases are only colored to make it easy for us to tell what color light will be produced" — while the actual light comes from semiconductor wavelength physics. A useful reminder that appearances often obscure what's really happening underneath.