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An electron is moving in vacuum and enters a region of space between parallel plates from the area’s upper edge so that the electron’s velocity is parallel to the plates (see figure). How big is the electron’s minimal possible speed vmin when exiting the area of space between the plates? The length of the plates is l and the distance between them is d. Between the plates there is a homogeneous electric field E, neglect edge effects. The electron’s charge is q and its mass is m. Neglect the gravitational force.