 Moselq8

2022-08-11

In addition to producing images, ultrasound can be used to heat tissues of the body for therapeutic purposes. An emitter is placed against the surface of the skin; the amplitude of the ultrasOund wave at this point is quite large.
When a sound wave hits the boundary between soft tissue and bone, most of the energy is reflected. The boundary acts like the closed end of a tube, which can lead to standing waves. Suppose 0.70 MHz ultrasound is directed through a layer of tissue with a bone 0.55 cm below the surface.
Will standing waves be created? wijnvatid

The condition for the standing wave to be created in a tube with open-closed boundary conditions is given by
${f}_{m}=m\frac{v}{2L}$...(1)
where m is an integer, v is the speed of sound through the given medium and Lis the length of the tube.
Given The length of the layer of the tissue is L = 0.55cm. The drequency of the wave is f=0.7MHz. The speed of sound through human tissue is $v=1540\frac{m}{s}$.
Calculatlon By using Eq. (1) and the given numerical values, we can find the value for the parameter m. If the value happens to
be an integer, a standing wave will be created. We find
$m=\frac{2Lf}{v}$
$=\frac{2\ast 0.55\ast {10}^{-2}\ast 0.7\ast {10}^{6}}{1.54\ast {10}^{3}}$
=5
We conclude that standing waves will be created.

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