A particle of charge -q and mass m enters a uniform magnetic field `vecB` (perpendicular to paper inward) at P with a velocity `v_0` at an angle `alpha` and leaves the field at Q with velocity v at angle `beta` as shown in fig.
A. `alpha = beta`
B. `v = v_(0)`
C. `PQ=(2mv_(0)sinalpha)/(Bq)`
D. particle remains in the field for time `t = (2m(pi-alpha))/(Bq)`
