1.

Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field vecB=B_(0)hatk.

Answer»

They have equal z-components of MOMENTA.
They must have equal charges.
They necessarily represent a particle, antiparticle pair.
The charge to MASS ratio satisfy :
`(e/m)_(1)+(e/m)_(2)=0`

SOLUTION :For a given pitch,
`P=(2pimvcostheta)/(Bq)`
`thereforeq/m=(2pivcostheta)/(PB)""...(1)`
(`theta` is angle of VELOCITY of charge particle with x-axis)
If motion is not helical `theta=0`.
As path of both the particles is identical and helical but of opposite direction in same magnetic field so by law of conservation of momenta,
`(e/m)_(1)+(e/m)_(2)=0`


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