PX156 - A1 - background

waves

u (x, t) = A \cos (k x \pm ω t)

e^{i (k x - ω t)} = \cos (k x - ω t) + i \sin (k x - ω t)

u (x, t) = R e (e^{i (k x - ω t)})

classical particles: position, $\vec{r} = (x, y, z)$ , and momentum, $\vec{p} = (m \dot{x}, m \dot{y}, m \dot{z})$