Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 17 - Waves-II - Problems - Page 511: 81a

Answer

The ratio of of the pressure amplitude of the wave in water to that of the wave in air is $~~59.7$

Work Step by Step

Note that $p_m = v~\rho~\omega~s_m$ We can find an expression for the intensity of a sound wave in the water: $I_w = \frac{1}{2}~\rho_w~v_w~\omega^2~s_w^2$ $I_w = \frac{1}{2}~\rho_w~v_w~\omega^2~(\frac{p_w}{v_w~\rho_w~\omega})^2$ $I_w = \frac{p_w^2}{2~v_w~\rho_w}$ We can find an expression for the intensity of a sound wave in the air: $I_a = \frac{1}{2}~\rho_a~v_a~\omega^2~s_a^2$ $I_a = \frac{1}{2}~\rho_a~v_a~\omega^2~(\frac{p_a}{v_a~\rho_a~\omega})^2$ $I_a = \frac{p_a^2}{2~v_a~\rho_a}$ We can find the ratio $\frac{p_w}{p_a}$: $I_w = I_a$ $\frac{p_w^2}{2~v_w~\rho_w} = \frac{p_a^2}{2~v_a~\rho_a}$ $\frac{p_w^2}{p_a^2} = \frac{v_w~\rho_w}{v_a~\rho_a}$ $\frac{p_w}{p_a} = \sqrt{\frac{v_w~\rho_w}{v_a~\rho_a}}$ $\frac{p_w}{p_a} = \sqrt{\frac{(1482~m/s)(998~kg/m^3)}{(343~m/s)(1.21~kg/m^3)}}$ $\frac{p_w}{p_a} = 59.7$ The ratio of of the pressure amplitude of the wave in water to that of the wave in air is $~~59.7$
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