# Plane wave onto a planar interface

1. Dec 11, 2008

### unstoppable

1. The problem statement, all variables and given/known data

A plane wave is normally incident on tthe planar interface with a medium of refractive index n but the interface moves, in the same direction as the incident wave, at speed u. If the incident wave's frequency is OMEGAo, what are the frequencies OMEGA1, OMEGA2 of the reflected and transmitted waves respectively?

2. Relevant equations

I believe these are the equations. incident wave: exp[j(omega*t-k1n*r)] in region 1
reflected wave: exp[(j(omega*t+k1n*r)] in region 1
transmitted wave:exp[(j(omega*t-k2n*r)] in region 2
The wave function at each point z is given by f(t-z/c).

k1=omega*sqareroot(mu1*epsilon1) and k2=omega*sqarereoot(mu2*epsilon2)

NOTE:* in the exponential=means the those are two vectors dotted with each other
3. The attempt at a solution

I tried using the incident wave formula and trying to find what k was by making k=2*Pi/Lambda, but I got stuck and didn't know what lambda was. I also tried using f(t-u*t/c) and making it equal to sin(omega*t). I'm not sure if that's corrrect. I'm lost and I really need someone's help because I have submit this assignment by tomorrow morning at 9 a.m.!

2. Dec 12, 2008

### turin

Is there a frame of reference that would simplify this problem?

3. Dec 12, 2008

### unstoppable

Hi well the only thing I have to work with actually is the wave function at each point z is given by f(t-z/c). Therefore in the problem I made f(t-ut/c) equaled to sin(OMEGA0*t) and I went on from there.