A positive charge 'q' of mass 'm' is moving along the +x axis. We wish to apply a uniform magnetic field B for time \[\Delta \,t\] so that the charge reverses its direction crossing the y axis at a distance d. Then:

\[B=\frac{2mv}{qd}\] and \[\Delta t=\frac{\pi d}{v}\]

\[B=\frac{mv}{qd}\] and \[\Delta t=\frac{\pi d}{v}\]

\[B=\frac{mv}{2qd}\] and \[\Delta t=\frac{\pi d}{2v}\]

\[B=\frac{2mv}{qd}\] and \[\Delta t=\frac{\pi d}{2v}\]

A positive charge 'q' of mass 'm' is moving along the +x axis. We wish

1.	A positive charge 'q' of mass 'm' is moving along the +x axis. We wish to apply a uniform magnetic field B for time \[\Delta \,t\] so that the charge reverses its direction crossing the y axis at a distance d. Then:
A.	\[B=\frac{mv}{qd}\] and \[\Delta t=\frac{\pi d}{v}\]
B.	\[B=\frac{mv}{2qd}\] and \[\Delta t=\frac{\pi d}{2v}\]
C.	\[B=\frac{2mv}{qd}\] and \[\Delta t=\frac{\pi d}{2v}\]
D.	\[B=\frac{2mv}{qd}\] and \[\Delta t=\frac{\pi d}{v}\]
Answer» D. \[B=\frac{2mv}{qd}\] and \[\Delta t=\frac{\pi d}{v}\]