How do I find E(d), the magnitude of the E field a distance d above a plane, using Gauss' Law?

A large sheet of plastic of dimensions LxL is charged with a uniformly distributed charge Q. If we approximate the sheet by an infinite plane, we can calculate the electric field it produces. Express the answer in terms of the givens in the problem. (You may also invoke universal constants.)How do I find E(d), the magnitude of the E field a distance d above a plane, using Gauss' Law?Consider a Gaussian surface in the form of an upright cylinder with base dA just below the surface on the opposite side of the point where we have to know E(d). let 2d be the height of the cylinder d above the surface up to the point and d below. The flux coming out of this surface = 2*E(d)* da which must be equal to (epsilon)o times the charge inside or

(Q/L^2)*(dA)(1/epsilon)o) = 2*E(d)*dA, where '(epsilon)o' is permittivity of free space = 8.85*10^-12 F/m or E(d) = [1/(2*8.85*10^-12)]*[Q/(L^2)] = (5.6*10^12)*[Q/(L^2)] N/C

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