# Homework Help: Where in a wineglass does the standing wave forms?

1. Feb 27, 2013

### 06mangro

Hi Im doing coursework relating to resonance in a wine glass,
and i am so confused as to where the standing waves are formed,
clearly in videos i have watched the wineglass, when exposed to a high amplitude of its resonant frequency (in slow motion) clearly shows the wine glass vibrating back and forth with the frequency of the sound wave, this is when next to a speaker.

Does the Same apply for when i rub my finger round the rim what about then??

Also what about when i fill the glass up with water, the frequency clearly goes down, is this related to the amount of material there is for the wave to travel in (less material for the wave to travel around when there is more water in it)?

How does the wave change as i fill the glass up?

Thanks xxxx
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2. Feb 27, 2013

### haruspex

A wine glass may have many modes of vibration. If you add water, it may shift the frequency of some modes, but it may also weaken some and strengthen others, so the change in pitch might be due to selecting different modes.
I would think that the frequencies produced by running your finger around the glass fairly represent the dominant resonances.

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