now we know that electric field at a point just outside the conductor for is E=(e0)/(surface charge density)

if u have resnick and halliday refer the section of a charged isolated conductor in the chapter gauss law.

the derivation is given.or u can refer any good book and see abt electric field outside a charged isolated conductor in gauss law chapter.

this is valid only for a point just outside a conductor.for faraway points from the conductor,it ceases to hold true.

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