Скачать или смотреть resonance standing wave wine glass a science with bobert video short

Dr. Smith has a wine glass that has no decorations and very thin walls. Such a wine glass will give a loud and clear sound when tapped and will create standing waves in the glass. However, creating standing waves in a wine glass is not as easy as it looks. rubbing a dry finger along the rim of the glass provides too much friction…..while rubbing a very wet finger does not have enough friction. Rubbing too fast does not work…. rubbing too slow does not work either……The finger must be rubbed along the rim of the glass with just the right amount of moisture, pressure, and speed in order for the the correct amount of energy to be transferred to the glass that perfectly matches the energy of the natural resonant frequency of the glass. Remember, standing waves are actual physical oscillations in the object, so Dr. SMith can only hold the glass at a node. If he holds the glass somewhere else, the standing wave will dissipate its energy into his hand stopping the generated sound.

You can easily change the natural frequency of a wine glass by adding water. The addition of wAter changes the mass of the glass and with more water a lower natural frequency resides in the glass. If you look closely at the edge of the water in a resonating glass you can standing waves being created!