If you are looking for something different to demonstrate the wonders of science, a new way to use a laser pointer, or a different type of experiment that you may not have considered – this may be of interest. The people behind the Treehouse Projects website have demonstrated how to carry an audio signal over a beam of light.
The concept is very simple – the analogue audio source (e.g. from the headphone socket of an MP3 player) is connected to a laser pointer via an audio transformer.
The audio waveforms are then converted to beams of light of varying strength. These are then received by a photoresistor at the other end, which converts the varying beam of light back to the matching audio signal. From this point you can then use the audio as normal, such as listen through headphones. The music can be simply muted by breaking the laser beam. You can see this audio-to-light bridge demonstrated in the following video:
As well as the instructions, the authors have left us with an explanation on the theory of operation including how audio transformers work and everything you need to know to get started with your own version. However if you do – take care with the laser beam and make sure the sharp beam can’t be seen by the human eye. To get started visit here: http://www.treehouseprojects.ca/audiolight/.