AP1200_Ch3_Waves-5Refr_Diffr_Beats_Doppler-2008

AP1200_Ch3_Waves-5Refr_Diffr_Beats_Doppler-2008 - AP1200 3...

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1 AP1200 – 3. Waves Concepts AP1200 – 3. Waves Concepts 3.5 Wave refraction and diffraction, 3.5 Wave refraction and diffraction, beats and Doppler effect beats and Doppler effect Michel A. Van Hove Michel A. Van Hove WARNING: PRINTING THIS DOCUMENT WILL USE MUCH INK AND WILL NOT SHOW ANIMATIONS.

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2 Wave refraction A wave front behaves like a row of people in which people at one end walk fast, and people at the other end walk slowly
3 Wave model: Note: at normal incidence (θ 1 = 0), the wave does not change its direction (θ 2 = 0)! Wave refraction at sharp boundary Wave refraction at sharp boundary D. Russell The refraction is a local event at the interface between different media See also http://www.walter-fendt.de/ph14e/huygenspr.htm Wave refraction is the change of direction of a wave due to a change of speed resulting from a change in the medium (support) Examples: - water waves entering shallower water - light entering water from air - sound entering less dense solid 8

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4 A change of speed causes a change of wave length , thus forcing a change of direction Important : a wave travels perpendicularly to its wave fronts (in most materials). Use: speed c = λ /T = λ f , so λ 1 = c 1 /f and λ 2 = c 2 /f (f = constant frequency = f 1 = f 2 ). Wave continuity requires: λ 1 /sin θ 1 = λ 2 /sin θ 2 (so wave peaks match wave peaks). If we know c 1 , c 2 and θ 1 , then θ 2 is determined: Wave refraction at a sharp boundary Wave refraction at a sharp boundary θ 1 θ 2 c 1 c 2
5 Light refraction at air/water/glass interfaces Light refraction at air/water/glass interfaces The angle of refraction depends on the angle of incidence Water and glass refract light about equally water/glass air 6

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This note was uploaded on 04/17/2011 for the course AP 1200 taught by Professor Michela.vanhove during the Spring '10 term at City University of Hong Kong.

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AP1200_Ch3_Waves-5Refr_Diffr_Beats_Doppler-2008 - AP1200 3...

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