Write the equation of displacement of an element of a medium in a harmonic wave.

(N/A) The displacement function for a harmonic wave is given by the equation: $s(x, t) = a \sin(kx - \omega t + \phi)$.
Here,$s(x, t)$ represents the displacement of an element of the medium at position $x$ and time $t$.
$a$ is the amplitude of the wave.
$k$ is the angular wave number,defined as $k = \frac{2\pi}{\lambda}$.
$\omega$ is the angular frequency,defined as $\omega = 2\pi f$.
$\phi$ is the initial phase constant.