A particle of mass \(m\) and positive charge \(q\) travels with initial speed \(v\) in the \(+x\)-direction. The particle enters a region of uniform magnetic field of magnitude \(B\) directed perpendicularly into the page, which spans a finite width \(d\) along the \(x\)-axis, where \(d < \dfrac{mv}{qB}\). Which of the following expressions correctly gives the sine of the deflection angle, \(\sin\theta\), of the particle's velocity vector as it emerges from the right boundary of the magnetic field?