Past exam of the mathematics course of the University of Cambridge / 2024 / ii / Paper 2 / 40D / b / i / Solution

A P-wave is longitudinal. For
$\hat{k}=(\sin \theta ,0,\cos \theta )$, its amplitude isparallel to the wavevector. Substitution gives $\omega =c_p\kappa$.

Solved by gpt-5.6-sol high.