Below I have posted both a photograph of the question (7) as diagrams are involved and figured it would be easier to take a photograph of my work to as it would be far too long to type:)
I hope it is clear to see what I have done in my working, it’s quite basic anyways but just incase……..
I first noticed that the only contributing flux would be that out of either side on the plane the positive and negative z direction, I then noticed that the plane was fixed on the z axis!
I then found the electric field of this square plane and having the electric field integrated from 0-L for the x and y components using gauss law:)
The only equations I used were that of Gauss, which are also on the working sheet
Apologies if the writing is unclear or my questions is unclear, I hope you can help it would be much appreciated 🙂
Thanks in advanced