Physics????

Question

I recall at school learning about when two things are oscillating at the same frequency - it has a name. It's what causes glass to shatter when opera singers hit the top note! Anyone can fill me in?

Answer 1

It's not necessarily that two things are oscillating at the same frequency. What you're refering to is HARMONIC RESONANCE.

Each object has a frequency at which it vibrates efficiently (in other words, when under impact of energy waves with that frequency, the particles actually magnify the vibration, increasing its intensity). This is the Resonance Frequency. It's next to impossible for a singer to hit a note that will resonate perfectly to destroy a crystal glass, but there are historical accounts of it occuring (it's not the volume of the singer, it's the magnified vibration feeding into itself until it shatters the crystaline structure of the glass). Resonant frequencies are also why your voice sounds different when you inhale helium rather than oxygen.

A brief experiment in resonance: take a crystal wine glass and hold it on a table by it's base (with your non dominant hand). Lick the pad of your index finger and apply a slight pressure to the rim of the glass. Run your finger around the rim of the glass. If you do this with the right pressure and speed the glass will resonate and you'll hear it make a tone (which varies from glass to glass depending on shape and how much liquid is contained in the glass). It's important to use a stemmed glass to make this easier, since a normal glass will have its vibrations damped by contact with the surface, making it harder to get volume out of the resonant frequency.

Answer 2

Resonant Frequency:

The resonant frequency of a wine glass can be found by 'pinging' it, much like pinging a tuning fork to hear its resonant frequency. To demonstrate the resonant frequency of the glass, first try the trick where you wet a clean finger, and rub it around the edge of the glass in circles, until the resonant frequency is excited and a tone is heard. It has been said that an expensive 'crystal' glass is needed for this, but it seems that it is very possible with any glass which is clean. Now measure the frequency accurately in order to carry out the demonstration. A microphone and an oscilloscope can be used to measure what this frequency is. With this knowledge, use speakers, driven with a pitch which matches this resonant frequency, at a high volume, to shatter the glass. The glass will shatter if the amplitude of vibration becomes too great. The volume will be annoyingly loud, so earplugs are advised. This is the set up below:

A number of different glass shapes will be experimented with, in order to see which one most consistently shatters. A set of different wine glasses, a flat, square pane of glass, a glass guitar slide, and even microscope strips, etc, will be experimented with until one is found which can be shattered consistently. The glass will shatter best if it is sitting on top of a sponge of some sort.

A strobe light can be used with this experiment. The frequency the audience will see when a strobe is flashing is the frequency of the vibrating glass minus the frequency of the flashing light. As the pitch increases and gets closer and closer to the resonant frequency, it will appear that the glass is decreasing in vibration. As the pitch becomes closer to the resonant, the amplitude of vibration increases, and eventually, at a pitch within approx. 0.5 Hz, the glass will shatter.

have the best of FUN!

Answer 3

In physics, resonance is the tendency of a system to oscillate with high amplitude when excited by energy at a certain frequency. This frequency is known as the system's natural frequency of vibration, resonant frequency, or eigenfrequency.

Answer 4

Resonance

Answer 5

When two things vibrate at the same frequency, they resonate

Answer 6

AP Physics is tough. If your math grades are at least a B then I would consider taking AP Physics. It will be tough for you unless you are really strong in math.

Answer 7

Resonance
You can find out more here http://en.wikipedia.org/wiki/Resonant

Answer 8

resonance

Answer 9

resonance

Answer 10

cause the fat lady sat on the glass thats why it breaks...