18. A particle with charge 9 and mass m is shot with kinetic energy K into the region between two plates as shown in Figure 9. If the magnetic field between the plates is B and as shown, how large must B be if the particle is to miss collision with the opposite plate?

(A) B = (2mK)1/2/qd,
(B) B = (2mK)1/2/2qd,
(C) B=(4mK)1/2/3qd,
(D)B=(3mK)1/2/2qd,
(E) B=(mK)1/2/qd.
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統計: A(1), B(0), C(0), D(0), E(0) #3207132
統計: A(1), B(0), C(0), D(0), E(0) #3207132