Uniformly Polarized disk on a conducting plane (E-Field)

1. Oct 9, 2011

jegues

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

A uniformly polarized dielectric disk surrounded by air is lying at a conducting plane, as shown in the figure. The polarization vector in the is,

$$\vec{P} = P \hat{k},$$

the disk radius is a, and the thickness d. Calculate the electric field intensity vector along the disk axis normal to the conducting plane (z-axis).

2. Relevant equations

3. The attempt at a solution

See the second figure attached for their solution and a picture of the problem, and the first figure for my attempt.

Are our answers the same? I can't seem to get it exactly in the form they have but it looks relatively close.

Can someone confirm?
Is my answer equivalent to theirs? If no what did I do wrong?

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2. Oct 10, 2011

lightgrav

your E1(z) is ok, your E2(z) is ok. your re-writing of them , as they are added, makes them seem more complicated, rather than terms canceling (to simplify).