Hello at physics lectures we wrote a phase of a sine wave like this:
$$\phi = kx - \omega t$$
Is this right? As I recall the phase of a wave should be written like this:
$$\phi = \omega t - kx$$
And if a wave changes direction $(k \rightarrow -k)$ like this:
$$\phi = \omega t + kx$$
Can someone explain to me if first usage is even possible and when if so.