Transmitting sound via a blinking LED using two 2p coins solar cell
Audio signals from the radio are carried by the LED light making it flicker. The flickering light then hits the solar cell, in this case an electrochemical cell with two electrodes submerged in an electrolyte solution (salt water). One coin has been oxidised to form copper(I) oxide or cuprous oxide which is a semiconductor by heating it strongly using a bunsen burner & gently removing the black copper(II) oxide layer. Similarly to a silicon based solar cell, when light shines on the cell, it generates an electrical signal that is synchronised with the flicker of the LED. Finally, the signal is amplified and the original sound is heard coming out of the amplifier/speaker.
A lovely demo to show long-distance communication, high-bandwidth communication lines for computers using modulated light signals.
Thanks to Christopher Chiaverina for sharing his article with me & inspiring me to make my own demo.
Reference:
Christopher J. Chiaverina, Kolchi Ishikawa, Norihiro Sugimoto, ''Light-wave Communications Using a Two-Cent Solar cell'', The Physics Teacher, Vol. 62, #3, March 2024, p. 236.