Aplha Particle in a magnetic field

[physicist101]

Homework Statement

An alpaha particle of charge q is released from a radioactive source and enters a vacuum where there is a unform magnetic field directed perpendicularly into the page, explain why the alpha particle follows a circular path.

Homework Equations

There is a picture of the page attatched

The Attempt at a Solution

Not quite sure, any help is appreciated, thanks.

 

[rock.freak667]

Firstly try to consider the direction of the force the magnetic field exerts on the alpha particle.

At any position in the magnetic field, use Flemming's Left Hand Rule to get the direction.