Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field `vec(B)=B_(0)hat(K)`

Options

A. they have equal z components of momenta
B. they must have equal charges
C. they necessarily represent a particle antiaritcl pair
D. the charge to masss ratio satisfy `(e )/(m)_(1)+(e )/(m)_(2)=0`

Answer

D

Explanation

In a uniform magnetic field the two charged particles will traverse identicla helical path in a completely oppsoset sense if the charge / mass ratio of these two articles is ame and charges on them are of opposite character in this situation `(e//m)_(1) +(e//m)_(2)Q` holds good