In my intro Electromagnetism physics class, one of the labs we did was really fascinating. I didn't have a huge amount of interest in it at the time so I don't remember the details of how it worked but now I really want to know. From what I remember the set up was like this: We hooked up a microphone to some circuit with an LED. This LED would flicker depending on what sound was input into the microphone. The LED then was held up to what I remember as a solar panel or something similar. The solar panel was attached to another circuit with a speaker. Essentially it transferred the sound from the microphone to the speaker through the flickering of the LED. Does anyone have an idea of what this is called? I'm assuming it's related to fiber optics in some way but it was a very simple set up that looked like you could make at home with some electronic supplies. Any details would be greatly appreciated.