LEDs, or Light-Emitting Diodes, have come a long way since their humble origins in the early 1900’s when it was discovered that passing 10v through Silicon Carbide would emit a yellow glow (shout out to Henry Joseph Round for that discovery!). Fast forward about a hundred years and LEDs are everywhere; automobile head lights, smart phones, TVs, and quite fashionably in game console modding.

Let’s dive in to LEDs!

The Basics

What exactly is an LED, anyway?

An LED is a special type of diode (which in-turn is a type of semiconductor) that emits photons when current is passed through it. Depending on the material or combinations of material used, different wavelengths can be produced allowing us humans to see different color light. LEDs can produce nearly every visible color between infrared to ultra-violet.

Image depicting different types of LEDs. Credit: Wikipedia

Colors and Wavelengths

Wavelengths are how we can measure “color”. Think of a wavelength as a point on a sliding scale where the start of the scale is the color blue and the end of the scale is red. As we move back and forth on the scale we can get different colors depending where we are in the spectrum. On our sliding scale, we can assign values to different ranges which are measured in “nanometers” (nm) – that’s 1 billionth of a meter!

ColorWavelength (nm)
Infrared700+
Red650 – 680
Orange600 – 640
Yellow / Amber580 – 600
Green520 – 550
Cyan490 – 520
Blue460-490
Ultra-Violet400-
Approximate color wavelengths.

In the next section will look a little closer at actual LEDs.