Date: Fri Jun 29 14:43:58 2001
Posted By: John Balbach, Physicist
Area of science: Physics
ID: 993614577.Ph
Message:
Your question is somewhat vague, and therefore difficult to answer. The
simplest answer is "nothing". There is nothing that will resonate at any
frequency without some sort of adjustment. Let me explain.
Resonance occurs when an external event excites a normal mode of the
resonating object. An object has a normal mode at a particular frequency
when a standing wave (a wave that reinforces itself, and so does not suffer
from self-cancellation) can be excited. This depends on certain physical
properties of the material, and on the size of the object.
Some examples:
- tuning forks have normal modes at their rated frequency. This
frequency is determined by the material (steel, aluminum and copper tuning
forks of the same size would have different frequencies) and by the size (a
set of tuning forks come in all sorts of different sizes.
- Radios are tuned to certain frequencies by varying the capacitance or
the inductance of a tuned circuit.
- Unpaired electrons and certain atomic nuclei will resonate at various
frequencies depending on the size of magnetic field that they sense. This
is called magnetic resonance. The resonant frequency is largely determined
by the gyromagnetic ratio of the nucleus (or electron) but also by the
environment around the nucleus (or electron).
I would have to know a lot more about what kind of resonance you are
looking to excite before I can suggest a material, shape or device. For
some reading on your own, you might try any introductory physics text, a
text about the physics of sound and music, or a book about Radiofrequency
circuit design.
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