Simple turning point of a variable-speed wave
= Simple turning point of a variable-speed wave
{title2=$Q(Y_s)=0,\quad Q\prime(Y_s)\ne0$}
A simple turning point for a stratified <wavespeed> occurs at $c(Y_s)=\omega/k$, where $Q=\omega^2/c^2-k^2$ has a nonzero derivative. If $c_Y(Y_s)>0$, write $q=-Q'(Y_s)>0$; then $\ell\sim[q(Y_s-Y)]^{1/2}$ below it. The vertical <group velocity> vanishes and the <stationary wave amplitude in a stratified wavespeed> diverges as $(Y_s-Y)^{-1/4}$.