Wave Properties and Propagation (4D) Practice Test

A neuroscience lab delivers a brief mechanical pulse along an axon-like hydrogel fiber to mimic a traveling disturbance. The pulse travels $0.30\ \text{m}$ in $0.10\ \text{s}$. The lab then switches to a different hydrogel with the same geometry but higher stiffness, and measures a travel time of $0.060\ \text{s}$ over the same distance. Which statement best describes the wave behavior in this scenario?

A clinician uses a pulse oximeter that emits red light and detects the returning signal after it passes through tissue. In a benchtop test, the same light source is used but the optical path is changed by inserting a slab of material with a higher refractive index $n$ than air. The light frequency $f$ is set by the source and remains constant. Based on the given conditions, what is most consistent with the observed wave phenomenon inside the higher-$n$ material?