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The Arduino Synthesizer
Easy, cheap portable VENTED fume extractor and optional fume box
How To Build A Vacuum Tube Tesla Coil (VTTC)
The basic execution is fairly simple. you want the laser pointer to aim through the water onto the wall. with his specific method, you will want to adjust the eraser until the height of the toothpick's tip and the height of the laser are about the same. As for why it works, the light from the laser hits the water droplet placed at the tip of the toothpick and refracts when it hits the drop of water. because the water has a round shape, the light refracts differently at each point and produces a reversed image on the back of the wall. This can be referred to as a liquid lens.