Demonstrate Understanding of Scientific Concepts and Principles Practice Test

An ultrasound transducer emits sound into soft tissue. At a boundary between two tissues, the intensity reflection depends on acoustic impedance $Z = \rho v$, where $\rho$ is density and $v$ is sound speed in the medium. Greater mismatch in $Z$ leads to greater reflection. If the beam encounters a boundary from muscle (moderate $Z$) to air (very low $Z$), which result is most consistent with this impedance principle?

A microfluidic device measures viscosity of plasma by driving it through a narrow channel at steady flow. For laminar flow, Poiseuille’s law gives volumetric flow rate $Q = \dfrac{\pi r^4\Delta P}{8\eta L}$, where $r$ is channel radius, $\Delta P$ is pressure difference, $\eta$ is dynamic viscosity, and $L$ is channel length. If $\Delta P$, $r$, and $L$ are held constant but plasma viscosity increases due to elevated fibrinogen, what change is expected for $Q$?