In my Appliance Science column for CNet, I look into the fascinating physics of LED lights. It’s all about electrons, quantum physics, energy levels and water flowing downhill.

And, like a waterfall, interesting things happen at this point where the flow is controlled. Whereas a waterfall makes noise, electrons flowing across the pn-junction of an LED release light. As the electrons flow from the n to the p layer, the energy level of the electrons falls, dropping from the higher energy level of the p-type layer to the lower one of the n-type. This energy is released as a photon, which we see as light.