Constructing an LED

Notice that on the left of the screen is an illustration of 6 different LEDs and a virtual circuit apparatus to explore the properties of LEDs as voltage on them changes. On the right of the screen are the two blocks of material that make up the LED chip with an energy scale and output spectrum illustrated below the blocks.

In this program, we can:

When the voltage is appropriate, transitions (represented by a vertical arrow) will occur and light will be emitted. A spectrum will appear below the energy scale.