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Unformatted text preview: FNT #1 Introduction to waves August 9, 2005 1 FNTs 1 & 2 A 2-D wave created by dropping a stone into a pond The wave was caused by dropping the stone in. This creates a pulse wave: a wave that travels out and does not repeat (see the diagram with the slinky for an example of a pulse wave). This is because the stone sinks it does not bounce up and down generating new waves! The actual wave is made up of water molecules oscillating. No water molecules travel along with the wave, but a raising and lowering of different water molecules propagates across the pond. The wave is transverse. The wave speed is determined by the medium, which in this case is water. By changing properties of the water (such as the temperature or the depth) you can change the wave speed. The amplitude is determined (in part) by the amount of energy absorbed by the water from the falling stone. By dropping the stone from a greater height it has more kinetic energy when it hits and can create waves of a larger amplitude. Note: In the case of a pulse wave, the terms frequency, period and wavelength do not mean a lot as the wave does not repeat. The wave speed is still well defined 1 A swimmer bouncing up and down The wave is created by the swimmer bouncing up and down. The waves will have the same frequency as the swimmers oscillation. Parts b) and c) have the same answer as the pond. The waves are again transverse. The amplitude is determined by the amplitude of the oscillation of the swimmer. The higher and lower the swimmer bounces the greater the oscil- lation of the water waves. A person playing the flute Th wave is created by is caused by the person setting up pressure waves in the flute with their breathing. Breathing generally produces many different frequencies, but the ones that survive are the ones that are not significantly damped by the flute. These are called the resonant frequencies or the har- monics . By opening and closing different holes on the flute with your fingers you change the resonant frequencies of the flute (we will discuss this more when we talk about nodes and anti-nodes)....
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