question_answer 63)

  Consider an electron in front of metallic surface at a distance d (treated as an infinite plane surface). Assume the force of attraction by the plate is given as  Calculate work in taking the charge to an infinite distance from the plate. Taking d = 0.1 nm, find the work done in electron volts. [Such a force law is not valid for .

Answer:

                    Refer Fig. 7(EP).3, Let the electron be at distance x from metallic surface. Then force of attraction on it is  Work done by an external agency for a displacement  against the force of attraction  is, Total work done by external agency in taking the electron from distance d to infinity is