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I was doing a question, in this i have to find distance between proton and plate.. so i use work energy theorm ie change in ke is net work done..

so as for electric field i use gauss law and taken gauss surface as cylinder.. through which i find electric field '$\sigma/2\epsilon$'.....

so $$KE = qEd$$ $$(E= \sigma/2\epsilon)$$

and got my ans 80 mm but the real ans is 40 mm....

after going through solution i come to know that E=$\sigma/\epsilon$.. but why? this Electric field is used when there is no electric field on other side.. but other side also have electric field.. so my solution must be right...

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  • $\begingroup$ Some comments removed. Please remember that comments are not for answering questions. $\endgroup$
    – ACuriousMind
    Commented May 1 at 8:34

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