I am really confused over this actually! Please don't mind.
When I started this and encountered this fact of 2 I went for to know why this 2 comes. There I saw the derivation and find that this derivation is done over a charged surface considered to be a charged sheet having two surfaces! Now...
Yes I am getting that! But not really satisfied! Ok I understood this bound charge is working as a free charge! But why not to consider permittivity is not clear to me! I mean is there any exact physical reason behind this?
This confusion is about the following problem:
Suppose the entire region below the plane z=0 is filled with uniform linear dielectric material of susceptibility ##χ_e##. Calculate the force on a point charge q situated a distance d above the origin.
Now, this problem is done in Griffiths'...