Intensity of Electromagnetic Wave

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

Show that intensity of radiation(EM wave) falls off with depth z
I(z)= Ie^(-2niwz/c)

where I = initial intensity
and ni=complex paert of refractive index

2. Relevant equations
I have tried the solving the solution using poynting vector.

I have been pondering over the question over the last two days without any success. I think i am making it more complicated than it needs. to be. I would appreciate it if you point me in the right direction .


Homework Helper
Determine the electric field. You are probably supposed to assume that an EM wave is normally incident on the surface.

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