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Resonant frequency fun

If you have ever rubbed a clean, wet finger on the edge of a wine glass, you may have heard the wine glasses make a singing sound. They say you can't hear pictures, but I bet you can hear this one! Ray Petelin As your finger moves along the rim of the glass, it sticks and slides. This causes the glass to vibrate. According to if you reach the glass's resonant frequency, or the natural frequency at which the glass will vibrate the most and create a sound of the same frequency. You can change that frequency by adding or removing water. This makes the sound higher and lower in the glass by changing the resonant frequency and lowering the pitch. A simple experiment that you probably have seen before. We are going to take this experiment an additional step. Alright, right now, there are no vibrating molecules in the air, so it's quiet! Ray Petelin We can't hear anything if molecules in the air aren't vibrating. We know the glass is vibrating to create a sound, but those sound waves are traveling through the air molecules for us to be able to hear them. This means, if we have another glass with a similar resonant frequency, we can send vibrations from one glass to another through the air. So we need another wine glass. Some call this a party, I call it science! Ray Petelin If we set the glasses next to each other, but don't allow them to touch. Make sure to fill them as close to the same amount as you can. Set a toothpick or two on the rim of one of the glasses. This toothpick is key to our high-pitched experiment. Ray Petelin Then, wet your finger and create sounds with the other glass. You will see the toothpicks fall into the glass! This happens because the vibrations from one glass travel to the other through the air. Down goes the toothpick! Ray Petelin Since they both have the same resonant frequency, they both vibrate! You can test your friends by saying you bet they can't make the toothpicks fall into the glass without touching or blowing them in. When they can't figure out how to do it, perform the experiment. Sweet music and science!