According to the findings of quantum mechanics with the electron localization inside the sphere of radius 10 ^ -10 m of its electric charge can be distributed in terms of density p = e / (2pRr2) * sin2 (2pr / R), where e - electron charge, r - distance from center of the sphere. Determine the strength of the electric field at a distance r = R / 2 from the center of the sphere.

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