A particle of mass m and charge q is projected with speed v into a uniform magnetic field B perpendicular to v. The pitch of the resulting helical path if the particle enters the field at 60° to B is
Correct: B
Pitch = v∥·T = v cosθ·(2πm/qB). With θ = 60°, cos60° = ½ → pitch = πmv/(qB).