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Two charged particles traverse identical...

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

A

They have equal z-components of momenta.

B

They must have equal charges.

C

They necessarily represent a particle, antiparticle pair.

D

The charge to mass ratio satisfy :
`(e/m)_(1)+(e/m)_(2)=0`

Text Solution

Verified by Experts

The correct Answer is:
D
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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