LEDs or light emitting diodes are everywhere from traffic lights to Christmas ornaments to remote controls.  Inside these tiny bulbs is a small grey block which is made of silicon. And, silicon has the unusual origin of coming from sand.

Sand is melted and purified and then cast in long thick logs, called ingots, which are slice like baloney. Twenty years ago, these logs used to be as thick as a thumb, now these logs are wider than dinner plates.  The slice is then cut into small square chips.

The chips are then given a bit of phosphorus on one side and a bit of boron on the other. Phosphorous is an element that has more electrons than silicon; boron has fewer electrons than silicon. These different sides are connected to a battery. The battery pushes electrons from the phosphorous side to the boron side. And, when these electrons connect with atoms that don’t have electrons, light is given off.

LEDs are more efficient than incandescent bulbs. Incandescent bulbs, the ones we attribute to Thomas Edison, give off lots of heat. This is why toy oven use these bulbs to bake small cakes.  In fact, 70 percent of the energy used by incandescent bulbs is heat. That’s wasted energy.

But, LEDs run cool. They are so cool that cities now must remove snow from LED traffic lights during the winter. In the past, incandescent bulbs ran so hot, they would burn off any snow that landed on them. LEDs are not running hot and so snow collects on traffic lights. (This happens when you solve one problem, you inherit another one.)

So, as you can see, small bits of beach sand purified into silicon are made into sandwiches that give off light. Now, this is a bright idea.

 

Additional reading & activites (Affiliate Links):

Elements: A Visual Exploration 

Snap Electronics Fun LED kit

Materials: A Very Short Introduction

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