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Unformatted text preview: 1 Physics 231 General University Physics Lecture 40 Lecture 9 1 Last Meeting Superposition & Interference Lecture 9 2 Today Standing Waves Lecture 9 3 Reflection of Waves (Fixed End and Free End) Demo: Propagating Torsion Wave Lecture 9 4 Standing Waves Given: two waves with the same amplitude, frequency and wavelength, traveling in opposite directions in a medium y 1 = A sin ( kx t ) and y 2 = A sin ( kx + t ) They interfere according to the superposition principle y= y 1 + y 2 The resultant wave is y=(2A sin kx) cos t Lecture 9 5 Superposition of Traveling Sine Waves 2 Lecture 9 6 Standing Waves (cont.) y = (2 A sin kx ) cos t Factorizes into f(x) g(t) Each point oscillates like a SHO At each instant, we have a sine wave This is the wave function of a standing wave There is no kx t term, and therefore it is not a traveling wave In observing a standing wave, there is no sense of motion in the direction of propagation of either of the original waves...
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- Spring '08