By Savoan Sereyboth and Ie Porchoung
Audio signals can be carried in radio waves through space and in electrical pulses through wires. Other forms of electromagnetic radiation, including visible light, can carry audio signals, too. You can build a simple device in which the signal from a radio is transmitted on a beam of light traveling between a light-emitting diode (LED) and a solar cell.
Modulated LED - Listen to a beam of light
