An electron does not suffer any deflection while passing thr

An electron does not suffer any deflection while passing through a region. Are you sure that there is no magnetic field?

Solution

The magnitude of the force F acting on a charged particle q moving in a uniform magnetic field B with a velocity v is given by F = qvB sin
where is the angle between the direction of the velocity of motion of the charged particle and the direction of the magnetic field.
The force will be zero when = 0 or 180° (sin 0 =sin 180° = 0) i.e. when the electron moves parallel or antiparallel to B, it goes undeflected.
Therefore we can say that the electron will not suffer any deflection on passing through a uniform magnetic field when the direction of motion of electron and direction of the magnetic field is parallel or antiparallel.
The magnetic field should be parallel or antiparallel to the motion of electron causing zero magnetic force on the electron so that it suffers no deflection.