An election moving with a speed u along the positive x-axis at y = 0 enters a region of uniform magnetic field which exists to the right of y-axis. The electron exits from the region after some time with the speed v at coordinate y, then

Force on the electron is given by F →=(-e)v→×B→. Direction of F →is along negative y axis.Hence y will be less than zero.The trajectory will be circular as shown .also since magnetic force does not perform any work on the electron , its speed remains unchanged.hence v=u.