Descriptors crest(positive), trough (negative), wavelength, amplitude

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1 Review of Waves Definition transfer of energy through a medium Pulse single disturbance Wave repeated or periodic disturbance Medium a substance or material which carries the wave Particle displacement zero particles are briefly disturbed before returning to their rest or equilibrium position. Basic Types of Waves Transverse, Longitudinal Transverse particles move perpendicular to the energy Descriptors crest(positive), trough (negative), wavelength, amplitude Longitudinal particles move in the same direction as the energy Descriptors compression, rarefaction, wavelength, amplitude Other types exist surface waves, complex waves, etc. **all waves can be mapped to a transverse wave which is identical mathematically to a sine curve therefore most waves are studied as a sine curve. Positive and negative numbers can be assigned to its amplitude Speed of a wave Medium dependent most waves travel at a specific speed in a given medium ex. Sound and light Equation for speed of sound temperature Equation for speed of light medium Key terms frequency, period, wavelength Amplitudehas no impact on the speed of a wave. Amplitude will decrease over time due to an energy loss. Energy is directly proportional to the square of the amplitude. Velocity = displacement/time, wavelength is defined as a length/cycle, period is defined as a time/cycle. Therefore, Derive the wave equation in terms of v,λ,t Define T in terms of f and replace in the wave equation Frequency is an inverse measure to period. Therefore, Wave problems often combine basic kinematics with the wave equation. 1

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3 Boundary Behaviour Reflection Waves exhibit definite patterns when they reflect. Fixed end reflection positive pulse returns as a negative pulse Free end reflection positive pulse returns as a positive pulse drussell/demos/reflect/ reflect.html Reflection and a Medium change Waves will also reflect when a medium has changed when entering a denser medium, the transmitted pulse reflects like a fixed end. When entering a less dense medium, the transmitted pulse reflects like a free end. Show entering a denser medium Reflection and direction When the reflecting surface as a defined shape the behaviour of the reflected wave also demonstrates a predicted pattern. Flat surface angle of incidence = angle of reflection Parabolic curve straight waves meet at the focus Diffraction a unique boundary behaviour Waves will spread in all directions when given a chance this is called diffraction. 3

4 Refraction (Particle reflection/refraction) Refraction refers to the changing of direction of a transmitted wave when it enters another medium. Interference Recall that particles only transmit the energy. Therefore, when two waves meet, each particle has to represent both forms of energy and is displaced accordingly. This is called the principle of superposition. When the combined amplitude is increased the interference is said to be constructive. When the combined amplitude is decreased (crest meets trough), the said interference is said to be destructive. Special Interference Patterns Two point source for a specific frequency English/2wa_tmp.htm Standing wave collision of two identical waves (frequency and amplitude) recall that the speed is medium dependent. key terms nodes, antinodes or loops Doppler Effect illustrates how the characteristics of a wave change when it is moving. galileoandeinstein.physics.virginia.edu /more_stuff/flashlets/doppler.htm Phase A description for the relative position in a cyclical or wave motion. Because one complete wavelength is described as 2π radians or 360 degrees, the phase of a wave is given in radians, degrees, or fractions of a wavelength. 4

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