Modern

The sound of light
You'll need a solar cell, and a headphone or microphone jack. Take the headphones or microphone off the jack, and wire the solar cell to the leads (make sure you strip the clear lacquer off the leads and test which is hot/common). Plug the jack into the line in on our soundcard, or straight into a cheap amplified speaker (must be amplified). If going to your sound card bring up software that lets you hear and playback the input from the microphone. Then the fun begins. With fluorescent lights (60Hz) you'll get a nice buzz when you turn the lights on that goes away when you turn the lights off. If you keep the lights offf and wave a laser pointer at the cell you can get it to clip in and out as you change the light intensity which the computer thinks is a change in loudness. Lots of variations, but it is a nice piece of demo equipment to have. An incandescent light will make no noise (no change in brightness). So the "trick" is that it is a change that is required, not just light itself.

Use a pocket comb to 'saw' across the laser beam. You hear the modulation change as the speed of the 'sawing' motion changes.