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Lost_student

Joined: 10 Apr 2011
Posts: 2
Location: Lost

 Posted: Sun Apr 10, 2011 10:50 pm    Post subject: A Wave travels Can someone help me with this problem I cant seem to make heads or tails of it. This question came from the Biological Physics book A wave travels from air (Zair = 413 kgm−2 s−1) into a liquid and with a density of 950 kg m−3 and in which the speed of sound is 750ms−1. (a) What proportion of the wave is reflected from the boundary? (b) What proportion of the wave is transmitted through the boundary? Many thanks in return for your help
hepcj

Joined: 23 Jun 2007
Posts: 125

 Posted: Mon Apr 11, 2011 10:59 am    Post subject: First you need to work out the acoustic impedance of water which is the density x the speed of sound. Z_liquid = p_liquid x v_liquid = 712500 kg m^-2 s^-1 a) The reflection coefficient is then (Z_liquid - Z_air)/(Z_liquid + Z_air) = 0.998841 so about 99.8% of the sound wave is reflected. b) The transmission coefficient is 2Z_air/(Z_liquid + Z_air) = 0.00116 or 0.12% is transmitted.
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