Chapter Objectives and Summaries
for the Oxford University Press text by Walding, Rapkins and Rossiter:-
" NEW CENTURY Senior Physics - Concepts in Context "
CHAPTER 13 Wave motion in one dimension
Knowledge of subject matter
- Describe how waves are created
- Distinguish between the types of waves - transverse and longitudinal
- Explain how waves carry energy and where this energy comes from
- Use and understand the meaning of th terms associated with waves - frequency, wavelength, period, troughs, crests, propagation, compression, rarefaction and velocity
- Use the wave equation v = f ÿ
- Explain the principles with regard to the transition and reflection of waves from fixed ends, open ends and from one medium to another
- Use the principle of Superposition of waves
- Identify a standing wave, means of creating such a wave, and identify parts of this wave - node, antinode, and wavelength
- Identify parts of waves from wave diagrams and determine the motion of particles of these waves
- Determine the speed, wavelength, and frequency of waves from graphical representations of waves
- Use the principle of Superposition to construct the resultant wave from two intersecting waves
- By using diagrammatic representation, construct a standing wave, or determine whether a standing wave will be produced
COMPLEX REASONING PROCESSES
- Solve novel problems associated with waves of an unseen nature
- Predict outcomes of pulse and wavetrain interactions on a spring at free and fixed ends.
CHAPTER 13 SUMMARY
- Mechanical waves are created by a disturbance in a medium and travels outwards from that point.
- Electromagnetic waves do not require a medium through which to travel and propagate at 3 x 108 m.s-1.
- Waves travel at a particular speed through a medium and different speeds through other media.
- When waves travel through a medium the particles of the medium vibrate either at right angles (transverse waves) or parallel (longitudinal waves) to the direction of propagation. They return to their original undisturbed position once the disturbance has passed.
- In transverse waves, the top of the wave is called the crest and the bottom is called the trough. The distance between two consecutive crests, or troughs, is the wavelength (l).
- Points in phase on a wave are any two points vibrating the same direction at the same time. A crest and a trough are 180o or ½.l out of phase.
- Longitudinal waves have compressions and rarefactions. The region of maximum particle density is the compression and the points of minium particle density is called the rarefaction. The wavelength is the distance between two consecutive compressions or rarefactions.
- The amplitude of a wave is the maximum displacement from the equilibrium or rest position, and is a measure of the energy carried by the wave.
- The frequency (f) is the number of waves generated, or passing a given point, per second, and is measured in hertz (Hz).
- The period (T) of a wave is the time for a wave to pass a point, T = 1/f.
- The wave equation - v = f.l, is used to determine the speed of a wave.
- Waves reflected from fixed ends are reflected out of phase with the incident wave.
- Waves reflected from free ends are reflected in phase with the incident waves.
- When waves meet the junction between two media they are transmitted and reflected. The transmitted wave is always in phase with the incident pulse. The reflected pulse is out of phase with the incident pulse if the second medium is more dense and in phase if it is less dense. The speed of the reflected pulse is the same as the incident pulse, while th speed of the transmitted pulse depends on the medium. The amplitudes of both the reflected and transmitted pulses will be less than the incident pulse.
- Superposition occurs when two waves meet. The resulting wave is obtained by adding the displacements of various points on the two waves.
- Stationary waves are created by superposition of a series of waves, having the same amplitude and frequency, and coming from the different ends of a medium. The continual addition and cancellation of the waves produces the standing wave pattern containing nodes and antinodes.
- Nodes are points of zero disturbance, and antinodes are points of maximum disturbance.
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