ID-UT AAPT 2010 Meeting Pocatello, ID.   http://physics.isu.edu/aapt/index.html 

I show a demo which relates voltage need to for an LED to turn on with the color of the light.  Physical Science 100 is a required GE class at BYU.  We are always looking for good demonstrations to represent the principles taught. This is being developed for Chapter 21: “Metals, alloys, and semiconductor” to illustrate the idea of a band gap.  I will show the effects with traffic light and UV flash light LEDs.   I will relate what is seen back to quantum mechanics and the photoelectric effect.