Figure 4 Measure the voltage across a zener diode with a digital multimeter. You can use the circuits in figures 2 and 3 to test LEDs, regardless of their color. Place the forward-biased LED you would ...

The increasing applications of LED ... using a high speed (il)luminance measurement device, or, for instance, a colorimeter, based on the implementation of the measurement devices and samples being ...

So, let’s get back to our task. It seems pretty easy: Take an LED (let's start with red), pass its light through the spectrometer, and use that to measure the exact wavelength of light.