A particle of mass `m` and charge `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 negative `z` direction, extending from `x = a` to `x = b`. The minimum value of `v` required so that the particle can just enter the region `x gt b` is

Options

A. `qb" "B//m`
B. `q(b-a)B//m`
C. `qa" "B//m`
D. `q(b+a)B//2m`

Answer

B

Explanation

`qvB=(mv^(2))/(R)` where radius R is `(b-a),` So `qB=(mv)/((b-a))` So `v_(m i n)=(qB(b-a))/(m)`