Quote:
The forward voltage of an LED is an attribute of the semiconductor used to create it, as is the color of the LED.

Specifically, each photon output gains its energy from precisely one electron input. The colour and the forward voltage are thus related by eV = hf, where e is the electron charge (1.6 x 10^-19C), V is the voltage, h is Planck's constant (6.6 x 10^-34 Js) and f is the frequency of the emitted light.

Peter