Does the Sign of the wt Term in EM Wave Propagation Matter?

[km707]

We were taught in the vibrations and waves lecture course that the solution to the wave equation for traveling waves is of the form ψ(z,t) = Acos(wt-kz).
In the Electromagnestism course we learned that EM waves are traveling waves and have the solution E = E₀cos(kz-wt).

I know that changing the sign of the z term determines the direction of propagation along the z axis, but does that mean that the "-wt" term correspond to moving back in time? Or does the sign of the wt term not matter?

Thanks!

 

[enricfemi]

for the cosine function,
cos(kz-wt)= cos(wt-kz)

so it equals the a change of direction in space z.

does it answer you question?

 

[Vanadium 50]

I don't understand what enricferni is saying.

cos(x) = cos(-x), right?

So cos(wt-kz) = cos(kz - wt). They mean exactly the same thing.