For an ultrasound wave with incident intensity 6.5 × 10^-2 J cm^-2 s^-1, what is the intensity of a beam reflected off a flat interface between muscle tissue and bone? The acoustic impedance value for muscle is Z_m = 1.66 × 10⁶ rayl, and for bone Z_b = 6.73 × 10⁶ rayl.

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Quizplus · Accepted Answer

The intensity of the reflected beam can be calculated using the reflection coefficient (R), which is given by the formula $R = \left( \frac{Z_2 - Z_1}{Z_2 + Z_1} \right)^2$, where $Z_1$ and $Z_2$ are the acoustic impedances of the two media. Substituting the given values for muscle ($Z_1 = 1.66 \times 10^6$ rayl) and bone ($Z_2 = 6.73 \times 10^6$ rayl), we find $R$. The reflected intensity ($I_r$) is then $R$ times the incident intensity ($I_i$). Calculating with the given incident intensity of $6.5 \times 10^{-2} \, \text{J cm}^{-2} \text{s}^{-1}$, we find the reflected intensity to be $3.93 \times 10^{-2} \, \text{J cm}^{-2} \text{s}^{-1}$, which corresponds to choice B.

For an Ultrasound Wave with Incident Intensity 6