$y = r$ sin $(\omega t - kx)$ There $\omega t =$angle $\therefore\ \ \ \ \omega = \frac{1}{T} = T^{- 1}$ Similarly $kx =$angle $\therefore\ \ \ k = \frac{1}{x} = L^{- 1}$ $\therefore\ \ \ \frac{\omega}{k} = \frac{\lbrack T^{- 1}\rbrack}{\left\lbrack L^{- 1} \right\rbrack} = \lbrack LT^{- 1}\rbrack$