A particle of the mass ` m ` and cgharge ` q` moves with a constant velocity `v` along the positive ` x`- direction . It enters a region containing a uniform magnetic field `B` directed along the minimum value of `v` required so that the particle can just enter the region ` xgtb` is

Options

A. `(qbB)/(m)`
B. `(q(b-a)B)/(m)`
C. `(qaB)/(m)`
D. `(q(b+a)B)/(2m)`

Answer

B

Explanation

`(mv^2)/(r)=qvB` or `(mv)/(b-a)=qB` or `v=(qB(b-a))/(m)`