# Allowed EM waveforms

• Rahulrj

## Homework Statement

which of the following proposed space-time dependent electric fields in vacuum is/are allowed by the equations of EM theory?
a) $$E_x=E_1\sin(kz-wt),E_y=E_2\sin(kz-wt),E_z=0$$
b) $$E_x=E_1\sin(kz-wt),E_y=2E_1\cos(kz-wt),E_z=0$$
c) $$E_x=E_1\sin(kz-wt),E_y=0,E_z=E_2\sin(kz-wt)$$

## Homework Equations

$$E = E_0\sin(kz-wt)$$

## The Attempt at a Solution

I think all the three equations are allowed according to the normal waveform. However I do not know what exactly to look for in such case that does not make it an allowed waveform. I would appreciate if someone could show an example that is not a waveform if my answer turns out to be correct.

Hello Rahulrj, What are
the equations of EM theory
?

I'm afraid your relevant equation doesn't mean much in the context of this problem. Anyway: what are all those symbols referring to ? You write vectors and scalars the same way ?

Hello Rahulrj, What are

?

I'm afraid your relevant equation doesn't mean much in the context of this problem. Anyway: what are all those symbols referring to ? You write vectors and scalars the same way ?
I do not know how to identify the allowed wave form and 'the equations of EM theory' idea doesn't help me much since I do not know what I require to distinguish an allowed waveform. $$E_x E_y$$and$$E_z$$ are electric field components,that's how the question itself is given.

The equations of EM theory are called the Maxwell equations, as I suspect you are supposed to know (from the fact you are given this exercise)...

The equations of EM theory are called the Maxwell equations, as I suspect you are supposed to know (from the fact you are given this exercise)...
I do know Maxwell equations but I am not sure how to make use of them to know the allowed waveform which is why I said that it doesn't help me much.

Do you now how to transform the maxwell equations into a wave equation ? Then you can check if the given ##\vec E## can satisfy such equations...

Do you now how to transform the maxwell equations into a wave equation ? Then you can check if the given ##\vec E## can satisfy such equations...
I don't think I understand that could please provide an example?
$$\nabla.D = \rho$$
How do i transform this?

In vacuum ##\rho = 0##...