Normal component of the electric field caused by a planar charge distribution

Example I Normal Component of the Electric Field Caused by a Planar Charge Distribution 

Suppose that there is a surface charge distribution on a plane surface a shown in Fig. 1.5. Let us introduce a vector dS  

Thus the normal component of the electric field can be written as  

Returning again to the calculation of the normal component En (Fig. 1.5), we can write it as  

In particular, if the charge is distributed uniformly on the surface (S = const) we have 1 

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