Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field B = B0 \(\widehat k\).
1
They have equal z-components of momenta.
2
They must have equal charges.
3
They necessarily represent a particle-antiparticle pair.
4
The charge to mass ratio satisfy : \({\left( {\frac{e}{m}} \right)_1} + {\left( {\frac{e}{m}} \right)_2} = 0\).