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Unformatted text preview: wavelength amplitude crest trough amplitude wavelength Chapter 11: WAVES AND SOUND Part 1: Introduction Wave motion is the transfer of energy from a source to a distant receiver without the transfer of matter between the two points. Waves are an oscillation that moves through a medium. In our work we will be working with waves that are rhythmic (occur regularly). Mechanical waves require a material medium for their propagation. They are disturbances in the equilibrium positions of matter. Examples would include sound waves and water waves. There are two requirements for a mechanical wave: a source of energy and an elastic medium. Electromagnetic waves dont require a medium for their travel. An example would be light waves. Waves can also be classified by how the particles in a medium are affected as the wave moves through a medium. Below, the parts of a transverse wave are shown on the left and of a longitudinal wave on the right. As the wave travels through the medium in a transverse wave, the individual particles vibrate from side to side perpendicular to the direction in which the wave travels. In a longitudinal wave the particles moves parallel to the wave direction. Equilibrium position A wavelength is the distance between two identical positions on the wave. In equations, the symbol for wavelength is the Greek letter lambda . The standard unit for wavelength is the meter (m). The frequency of a wave is the number of waves that pass a point per unit of time. The standard unit of time is the second. In equations, the letter f will represent frequency. The Greek letter nu is used by some books. The standard unit of frequency is the hertz (Hz). (A hertz is the same as 1 s or s-1 .) The crest is the highest point in a transverse wave and the trough is the lowest. On a longitudinal wave the compression is the area where the medium is closest together, and the rarefaction is where it is farthest apart. The amplitude of a wave is the distance from the midpoint to the crest or trough. The amplitude is related to the amount of energy the wave carries. We will not be using any equations with amplitude in them. The period of a wave is the time it takes for one wavelength to pass a point. The symbol for period is the Greek letter tau . The standard unit of time for period is the second (s). The equation that relates the period and frequency of a wave is: = 1 f p e rio d = in v e rs e o f fre q u e n c y To calculate the speed of something, the distance an object travels is divided by the time to travel that distance. In the case of a wave, if the distance traveled is one wavelength, the period of the wave is the time. With substitution, we end up with the following equation. The symbol for speed is the letter v ....
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- Spring '09