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 `xgtb` is

Options

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

Answer

B

Explanation

If `(b-a)ger` (r= radius of circular path of particle)
The particle cannot enter the regioin `x gtb`. So the enter in the region `x gtb`
`rgt(b-a)` or `(mv)/(Bq)gt(b-a)` or `vgt(q(b-q)B)/m`