This article from the Physics Teacher journal explores the possibility of constructing a light-wave communication system using a solar cell made from two pennies. The solar cell is actually a light-enhanced electrochemical cell, consisting of two copper electrodes, one of which is a light-sensitive semiconductor. The pennies are heated to produce cuprous oxide, which acts as the semiconductor. The solar cell is then constructed by placing the pennies in an electrolyte solution. An LED and a 3-V button battery are used to produce amplitude-modulated light, which is transmitted through the solar cell. The system is assembled by connecting a radio to modulate the LED, and the resulting varying cell output voltage is amplified and converted into sound. [Extracted from the article]