# Electric field as a function of time

## Homework Statement

Before diving into the quantum-mechanical superposition principle, let’s get some practice with superposition in classical physics. Consider an electromagnetic wave propagating in the z-direction, which is a superposition of two linearly polarized waves. The electric field vector in the wave is E = Ex + Ey, where Ex = a cos(kz − ωt), Ey = b cos(kz − ωt + δ). (1) The parameter δ is a real number between −π/2 and π/2, and indicates by how much the two components are out of phase. Look at the behavior of the electric field at some fixed value of z, say z = 0 for simplicity.

a) [2pt] Describe what the electric fields Ex and Ey are doing as a function of time.

E = Ex + Ey

## The Attempt at a Solution

Well I'm not really sure how to start the problem so I just tried to put it into complex form

Ex = a*ei(kz-ωt)/SUP]
Ey = b*ei(kz-ωt + δ)

Since they are separate components, I cannot add them together so I am unsure of what to do next

## Answers and Replies

BvU
Homework Helper
so I just tried to put it into complex form
Making things difficult, eh ? Why do so if you have an expression for ##E_x## and for ##E_y## as a function of ##z## and ##t## and the first part of the exercise asks for ##E_x## and ##E_y## as a function of ##t## for a given ##z## ?

Things may be more complex in part b) but I can't guess and you don't tell ...

Making things difficult, eh ? Why do so if you have an expression for ##E_x## and for ##E_y## as a function of ##z## and ##t## and the first part of the exercise asks for ##E_x## and ##E_y## as a function of ##t## for a given ##z## ?

Things may be more complex in part b) but I can't guess and you don't tell ...

Ah, so I can just set z=0 and I would have my function?

BvU