In a cathode-ray tube, electrons with an initial horizontal velocity v fly into the region of an electric field of length l, where they are affected by a vertical force from charged deflecting plates. What is this force equal to if the electrons hitting the screen are displaced by a distance y compared to the case of uncharged plates? The screen is located at a distance L from the center of the area of action of the electric force. The mass of the electron is m_e.