A charged paricle goes undeflected in a region containing electric and magnetic field. It is possible that

Options

A. `vecE||vecB` but `vecv` is not parallel to `vecE`
B. `vecv||vecB` but `vecE` is not parallel to `vecB`
C. `vecE||vecB`, `vecv||vecE`
D. `vecE` is not parallel to `vecB` and `vecv`.

Explanation

A charged particle will go undeflected in the electric field and magnetic field if the direction of force on particle due to electric field only acts in the direction of motion of the particle, i.e., the charged particles moves parallel to the electric field and magnetic field acts parallel to the direction of motion of charged particle. A moving charged particle will also not be deflected while passing through a region if the force on it due to electric field is equal and opposite to the force due to magnetic field. It will be so if magnetic field is `_|_r` to electric field and both the fields are `_|_r` to the direction of motion of charged particle.