# Electric field

Hi,

In electromagnetic wave, electric field take the form

E(z,t)=A q(t) sin(kz)

where A is a constant, k is a wave number, and q(t) is a time dependent factor having the dimension of length.

This mean that q is a position..but position of what ??

Is a position of the wave ?

vanhees71
No, $$q$$ is not a position but a time-dependen amplitude. What you have written down there is a standing wave. To get the solution, you have to plug this ansatz into the wave equation. This will give a simple ODE for $$q(t)$$, which you should be able to solve easily.