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 partical `-` antipartical parit
D. The charge to mass ratio satisfy `:`
`(e//m)_(1)+(e//m)_(2)=0`

Answer

4

Explanation

Since the charged particles traverse identical halical paths in a completely opposite sense in a uniform magentic field `B`, their radii` (r=mv sin theta//eB)` and frequencies `(v=eB//2pim)` must be equal For this `(e//m)_(1)=-(e//m)_(2) or (e//m)_(1)+(e//m)_(2)=0`