RI Chap 10 Wave Motion Lecture Notes

10 WAVE MOTION H2 Physics 9478 Content Page 10.1 Progressive Waves 2 10.2 Intensity of a Wave 10 10.3 Transverse and Longitudinal Waves 14 10.4 Polarisation 17 10.5 Appendix 20 Learning Outcomes Candidates should be able to: (a) show an understanding that mechanical waves involve the oscillations of particles within a material medium, such as a string or a fluid, and electromagnetic waves involve the oscillations of electromagnetic fields in space and time. (b) show an understanding of and use the terms displacement, amplitude, period, frequency, phase, phase difference, wavelength, and speed. (c) deduce, from the definitions of speed, frequency and wavelength, the equation vf λ= . (d) recall and use the equation vf λ= . (e) analyse and interpret graphical representations of transverse and longitudinal waves with respect to variations in time and position (space). (f) show an understanding that energy is transferred due to a progressive wave without matter being transferred. (g) recall and use the term intensity as the power transferred (radiated) by a wave per unit area, and the relationship intensity ∝ (amplitude) 2 for a progressive wave. (h) show an understanding of and apply the concept, that the intensity of a wave from a point source and travelling without loss of energy obeys an inverse square law, to solve problems. (i) show an understanding that polarisation is a phenomenon associated with transverse waves. (j) recall and use Malus’ law (intensity ∝ 2cos θ ) to calculate the amplitude and intensity of a plane polarised electromagnetic wave after transmission through a polarising filter.

RAFFLES INSTITUTION YEAR 56 PHYSICS DEPARTMENT Page| 2 10.1 Progressive Waves A wave can be described as a disturbance that travels through a medium from one location to another location. Waves can be considered as an energy transport phenomenon because energy is transferred from one point to another some distance away in the direction of wave propagation. This chapter will focus on progressive waves.  Wave Terminologies Displacement x of a particle is the distance in a specific direction of a particle of a wave from its equilibrium position. Amplitude 0x or A is the magnitude of the maximum displacement of a particle in the wave from its equilibrium position. Period T is the time taken for a particle of a wave to complete one oscillation. Frequency f of a wave is the number of oscillations made per unit time. Wavelength λ of a wave is the distance between two consecutive points which are in phase. Speed v of a wave is the speed at which the wave shape (or wave profile) moves. Phase φ of a wave is an angle that gives a measure of the fraction of a cycle that has been completed by an oscillating particle or by a wave. Phase difference φ∆ between two particles in a wave or between two waves at a point is a measure of the fraction of a cycle which one is ahead of the other. Wavefr