Wave Properties and Propagation (4D) Practice Test

A lab studies ultrasound transmission through soft tissue for imaging. A transducer emits a continuous wave at $f=2.0\ \text{MHz}$. In muscle, the wave speed is approximately $v=1540\ \text{m/s}$; in fat, $v=1450\ \text{m/s}$. The transducer frequency is unchanged when the wave crosses the boundary. Based on the given conditions, what is most consistent with the observed wave phenomenon at the boundary?

A biomedical device uses a vibrating membrane to generate a traveling wave in a fluid-filled microchannel. The driver maintains a fixed frequency $f$ while the device is tested in two fluids. In Fluid 1, the measured wavelength is $\lambda_1=1.2\ \text{mm}$; in Fluid 2, $\lambda_2=0.8\ \text{mm}$. Assume the frequency is unchanged between tests. Which statement best describes the wave behavior in this scenario?